An unfortunate piece of advice is to tell aspiring writers to develop a style. Aargh! No no no no no! That’s the LAST thing you should be doing. You can’t help having a style any more than you can help speaking with a particular accent. It’s literally not possible.
Now your writing might suck, but not because you don’t have a style. Maybe it SUX because you don’t understand subject-verb agreement or when to use apostrophes. Maybe it SUX because you try to be funny but aren’t, or are funny unintentionally. That equals SUX. It’s also true that lots of stuff that sux, sux in the same way – e.g., a lot of people don’t, in fact, know how to wield apostrophes – but what matters is the fact that it sux, not (only) the fact that it sux in a way that’s similar to other people’s sucky writing.
That’s a different problem from not having a style. If you’re “trying to develop a style,” you’ve got it all wrong.
Writing is a human mind on paper, and reading that writer’s work takes you into his/her mind. It takes you into their world. Borges was pure imagination and intelligence; his prose was crystalline (even in translation this is obvious) so you could perceive the ideas with no distractions. Heinlein was optimistic and folksy, and his amusing dialogue (after his first few stories) conveys this. Susanna Clarke is very English, at least from this American reader’s point of view, and is interested in what England circa 1800 would have been like if the old, dark fairy tales had been true. She explores this in the style of a novel of around that time. (Hence the comparisons to Jane Austen, if Austen had been on acid.) Bester was all about intense, driven characters, and his relentless, flooring-the-gas-pedal pacing is part of a style that matches his subjects. Lev Grossman, in The Magicians series, takes you into what magic would actually be like if actual North American twenty-something hypersmarties actually got their hands on it. He presents his fictional world with asides about particle physics and cellular automata, the way they’d view it. And so on.
The point is: If you self-consciously “try” to develop a style, you’re muting your own unique view of the world. DON’T DO THAT! Let your own style, your own take on things, flow out of you naturally. It’s one of your few items of stock in trade, and the only one on which nobody else can compete with you.
You don’t have to limit yourself to one kind of work. You can (and probably should) write humor and drama, etc. But your kind of humor story and your kind of drama story should – must, if you are to be any good – be yours, naturally yours, not the result of you trying to do something other than write naturally, the way [insert your name here]’s mind writes.