My advice is to write often and read critically across genres. When I say critically, I mean that you should read to understand the author's syntax, tone, diction, use of figurative language...the list goes on.
But I like to believe that one's writing style is intrinsically unique, and so the purpose of this should be to allow your writing to become more nuanced, not to write exactly like them. Here is something for you to try. One exercise that can help embody the mind of another writer is to write on a topic in his or her style; emulate the style completely by copying the syntax and word choice precisely. Pick a piece that you're currently interested in, and use that piece as your source material. It will probably feel foreign to you, which is the point: while it'll help you to understand the writer that you're interested in, you won't magically begin to write like that author.
That being said, you should, through the process, see your own style come forth as you begin to modify the prose with your own flair, as will undoubtedly happen when you read something that feels forced and stilted. I'd call that your emerging style, and it will become crucial as you begin to write your own essays. You shouldn't want to be someone else, but by trying to, you might find what makes you "you" as you discover the aspects of their style you like and the aspects you dislike.