Karma is of three kinds:
vachik (related to speech)
Manasik karma means contemplation of the physical appearance (roop), qualities (gun) and pastimes (lila) of Krishna, devoting your mind to bhagvat chintan leaving all else.
Vachik karma means speaking only what is spiritually beneficial to others, spiritually motivates others and describes the roop, gun, lila of Krishna.
Kayik karma means doing everything with the intention of pleasing Krishna. For instance, when mothers cook for children and family, it is a worldly deed and binds them in materialistic desires and its results. But suppose the same cooking done for pleasing Krishna, thinking 'I would make this dish for Krishna today', 'yesterday I offered Krishna this, today I will cook something different.' They cook thinking about Krishna and what Krishna would love to eat, in their love they imagine what he might like and dislike. And then serve the cooked dishes beautifully in vessels especially kept for Krishna and offer him with Tulasi. This becomes yoga, bhajan and helps cutting through the net of ignorance. If you think I must put some more chillies since my husband loves so or more spices since my children want it like that, then it is bhoga, materialistic deed with focus on your own senses and its pleasures. But the same action can lead you to Krishna Prem with the mere difference in intention! This is true for all of our actions. Dedicate all your actions for Krishna. The job you do is to earn money for service of Krishna and his devotees. Even the bhajan we do is for pleasing Krishna. We cannot free ourselves from materialism solely on our efforts of doing bhajan but since chanting harinaam pleases Krishna, we do it. The day we sacrifice all our desires and thoughts at the feet of Krishna, our bhajan is complete. Now we still chant your name just because it pleases you. The services we do for Krishna and his devotees is also just to please them and not with any intention of spiritual gain or salvation or even bhakti. We want bhakti of course, but not in return for the services. If the devotees and Krishna are pleased with my services, then I am already blessed with everything I need. If the devotees are not pleased and Krishna, who loves his devotees more than himself, is also not pleased, then my services have failed and I have made a mistake somewhere. This is called Sewa. It has to be niskam, free of material desires. And it has to be free from pride. Krishna is doing everything, making me a means of accomplishing his will. Just like a slave does everything for his master and accomplishes his orders and will. He has nothing to do for himself. He cooks for his master and whatever is left at the end becomes his meal. He accepts whatever food and clothing his master gives him and stays in the master's house. He has no say in any matter whatsoever. He has no demands or regrets. He has to be satisfied with whatever his master gives. Similarly, a true devotee has to be satisfied with whatever Krishna gives and do everything to please only Krishna. The day you will be able to do this your bhajan will be complete and you will be free from samsaar bandhan (the worldly ties). This is Samarpan. And it is very difficult.
Krishna says in Shrimad Bhagvat Gita:
"Tvameva sharanam gachchha sarvabhavena bharata,
tat prasadat param santim sthanam prapsyasi shashwata"
Take shelter of Krishna by all means, you will reach param santi, the blissful state of soul where no worldly matter can influence you, eternally.
"Tat karma hari tosham" means the action that pleases hari is a real action, all else binds you in the net of ignorance. Now you have to decide which actions may please Krishna and which may not.
"Yat karosi yad asnasi yaj juhosi dadasi yat,
yat tapasyasi kaunteya tat kurusva mad-arpanam"
O son of Kunti, all that you do, all that you eat, all that you offer and give away, as well as all austerities that you may perform, should be done as an offering unto Me.
"Subha asubha falairevam mokshyase karma bandhanaih,
sanyas yoga yuktatma vimukto mam upaisyasi"
In this way you will be freed from all results of good and evil deeds, and by this principle of renunciation you will be liberated and come to Me.
So offer everything you do to Krishna. Do each and every action only to please Krishna. Even tapasya, the austerities are to please Krishna and not for any personal benefit. If you do your actions with such mentality or pray to Krishna after an action that it is only to please him, then you have offered the action to Krishna.
What is tapasya? There are three types of tapasya: kayik, vachik and manasik.
"deva-dvija-guru-pragya-pujanam saucham arjavam,
brahmacharyam ahimsa cha shariram tapa uchyate"
The austerity of the body consists: worship of the Supreme Lord, the brahmins, the spiritual master, and superiors like the father and mother. Cleanliness, simplicity, celibacy and nonviolence are also austerities of the body.
Worship means to please them. Please Krishna, Gurudev, the brahmins or sadhus and vaishnavas and your elders. Cleanliness is of two types: internal and external. The absence of dirty or inhumane thoughts, absence of material desires, lust, anger, attachments, ignorance etc. in one's mind is called internal cleanliness. The mind should always be immersed in bhagvat chintan and the waves of outer world should not stir the mind. The outer cleanliness means keeping your body clean, washing hands after touching anything unclean, bathing and dressing yourself in clean clothes, etc. Arjavam means simplicity of mind and body. Forsake treacherous attitude, cunning thoughts, mismatch of what you think and what you speak or do, etc. Celibacy means brahmacharya. Women should not or minimise mixing with men and vice versa. The bodily constitutions of men and women are such and so powerful that they attract each other inevitably. It is inherent and natural. You just have to keep distance from the opposite sex. Remove even thoughts of the opposite sex from your mind. Ahimsa means nonviolence. Physical offence, hurting anybody intentionally, killing or beating anybody is physical violence. Speaking something that might hurt someone's sentiments or sadden them is spoken violence. Thinking about hurting someone or wishing bad about someone is mental violence. All three types of violence when forsaken you truly conform to nonviolence. These are the austerities of body.
"Anudvegkaram vakyam satyam priya hitam cha yat,
swadhyaya avyasanam chaiva vangmayam tapa uchyate"
Anudvegkaram vakyam means speech that doesn't hurt anyone. Maybe someone has done something wrong and you feel like saying some heated words to that person. But no, resist the force of words. It is tapasya. Satyam means the speech has to be true. Not hurting people doesn't mean that you will flatter anyone with ornamental lies. The speech should be true or just don't say anything. Priya means the speech should be good to hear. Speaking truth doesn't mean you will babble out hard and displeasing truths to others. Even if it is true but will hurt someone, just keep quiet. This is tapasya. Hitam means the speech should also benefit someone. It is true, it is good to hear and will not hurt anyone but it will not benefit anyone, then keep quiet, what is the point of speaking such a thing? It is a waste of speech. Resist the force of speaking that. This is tapasya. Use your power of speech in hari katha and describing roop, gun, lila of Krishna. That is swadhyaya avyasanam. These are vachik tapasya.
"Manah prasadah saumyatvam maunam atmavinigraha,
bhava samshuddhih ityetat tapo manasa uchyate"
Manah prasadah means the mind should be happy. It means accepting everything happening as Krishna's will and being undisturbed by any worldly matters. But we get disturbed by almost every single problem we face. Someone said something, we are upset. Something is lost, we are upset. Something is destroyed, we are upset. Something happened, we are upset. No. Don't let anyone or anything enter your mind, reserve your precious mind for your Ishtadeva, for Radha Krishna. Don't let any worldly matter enter your mind except Guru, Govind and Radharani. If worldly matters enter your mind, where will Yugal Kishore sit?
Once a person went to a sadhu and started accusing another person that he has thrown very insulting words at the sadhu, he has said this and that and the sadhu must not forgive him unless he begs pardon. The sadhu laughed at first. Then he said, "Oh, this person has thrown insulting words at me, you say? But, my dear, I didn't catch them! So what if he throws anything at me as long as I don't catch them?!"
Such is the mood of a real sadhu. But we catch the words. And hold on to them forever. This world is full of various kinds of people. Each and every person's thinking differs. For anything you do, some will agree and some will disagree. Just follow the scriptures and the teachings of great sadhus. Don't listen to what people think about it. You will never be able to please everyone. So what is the point in getting upset and quarrelling over things you can't change? Don't let these things enter your mind, the precious space for Radha Krishna to sit and play.
This world is full of shortcomings. There is no single creature that doesn't have any shortcoming. There is simply no point in analysing others' faults. Even Krishna could not change anything in this world. During his avataar time, he killed and gave moksha to so many demons until the very end. In Bhagvat Gita he says, "Dharma sansthapanarthay sambhavami yuge yuge". He established Dharma, removing the major evil doers and barriers of Dharma on earth. But as soon as he disappeared from earth, Kaliyuga took hold on earth and started ruling everywhere. What happened to the establishment of Dharma at that time?! Even Krishna could not change what is doomed to happen. So don't see others' faults and shortcomings. If you see, then you will not be able to chant harinaam and immerse yourself in bhagvat chintan undisturbed by worldly matters. That is why 'saumyatvam maunam', the stillness of mind at bhagvat chintan, is possible only when you cease finding faults in others and accept everything as Krishna's will. Atmavinigraha means retracting your mind from your senses and its pleasures and forcing it to bhagvat chintan. It is very difficult. We are naturally distracted to our senses and its attachments. We take pleasure in thinking about things we are attached to and our mind constantly wanders back to these attachments during our efforts to contemplate the roop, gun, lila of Krishna. Our senses seem to become only more active during bhagvat chintan and constantly distract our mind to every minute detail happening around us at that time! Retracting our mind from these things again and again and forcing it to bhagvat chintan is tapasya. Bhava samshuddhih means purification of our thoughts. Practice thinking the way a vaishnava should think. Having faith in Gurudev and all vaishnavas, humility at heart, observing everyone else as better than oneself, etc are part of bhava samshuddhih. This helps in immersion of mind in bhagvat chintan and achieving Prema bhakti. All these come under manasik tapasya.
A person who practices these three kinds of tapasya is a tapasvi. A tapasvi doesn't mean a person who stands all day and night on one foot! Such kind of bodily tapasya done out of material desire, with mind full of pride and stubbornness can give some siddhi, unnatural powers to the person, but he is very far from any kind of bhakti. Krishna has given you hands and legs for rendering service to Krishna and his devotees. If you waste it away unused like this, you might receive some unnatural powers now but in your next birth you will be deprived of those parts because you haven't used them for Sewa. The six enemies of jeevatma (kaam krodh lobh etc.) are residing inside his mind. How will such bodily tapasya help in destroying those enemies? Impossible. The three kinds of tapasya described above are real tapasya, wherein we fight with the six internal enemies and force our mind to bhagvat chintan, which is exactly what our enemies don't want us to do! And such tapasya pleases Krishna, so it is real karma too.