If it is an answer to a question that has the verb in it, each form is ok, like in: a) cosa ti piace fare ? b) mi piace lo yoga, fare 'trekking', e leggere un buon libro. Otherwise it is better to use the verb, i.e. 'fare yoga'.

Both are grammatically correct, depends on what you mean. If you like yoga or if you like doing yoga. "Mi piace" goes with verbs, things or people, almost everything! Mi piace mangiare, mi piace la pizza, mi piace Marta, mi piace quello/tu/lui.

Both the first and the second sentences are correct. The first one indicates that you like yoga the second one that you like to practice yoga. "Mi piace" usually refers to verbs but you can also says "mi piace il verde" I like the green color. "Mi piace il tuo nuovo vestito"--> I like your new dress etc.

Thanks everyone! I get it now =)