How do I talk about my hobbies in my essays?

You want to show the examiner that you have a good command of grammar and a varied vocabulary. So I would suggest including at least three hobbies and using a different verb each time you talk about a hobby. So, you could start your paragraph with: 'In my free time' (В свободное время...) followed by any of the following verbs to express preference:I like (to play tennis) - мне нравится (играть в теннис). I prefer (to play the piano) - я предпочитаю (играть на пианино). I love (meeting up with friends) - я люблю (встречаться с друзьями). I adore (reading books) - я обожаю (читать книги). Finally, try to use complex sentences by including connectives. So, with the first example above, your sentence will be even more impressive if you say:I like to play tennis because this sport is very intensive.Мне нравится играть в теннис потому, что этот спорт - очень интенсивный. Other connectives you could use are 'but' (но), 'and' (и), 'however' (однако), 'as, since' (так, как).