When someone does something good to you, say "Jazakallahu Khayran - May Allah reward you," instead of Thank You. It's not because Thank You is Haram or anything, but because Thank You does not physically benefit the other person in any way. While this prayer of yours is better

than any favor the person may have done for you.

Whenever a beggar would pray for our mother Sayyidah 'Aisha' (May Allah be pleased with her) for giving him money, she would pray for him as well. When asked, she would say that his prayer was worth more than the money, and hence she had to compensate with a prayer of her own.

Just stuff to think about.