Well, studying and avoiding those cliches would be a great start! And then, I guess you can simply do as other authors do whenever they are not familiar with a specific category of humans - ask one or more representatives of that category what they think about your character ideas and stolines, before launching yourself into drawing. Guaranteed, not all lesbians will have the same thoughts/perceptions about what being a lesbian means, but what else can you do, other than your own good homework?
One thing I would avoid, although it's apparently very popular is writing characters who "happen to be" female/males/gay/straight/Asian/Black/younameit. I think it's utter bullshit and very bland. If you are aiming for characters' depth, you have to keep in mind that sex, sexuality and race are at the very core of any human being, and if you just want to write them in the void, chances are you'll end up with ethereal junk.