As a general rule, fics with bad grammar/spelling drive me nuts, and also ones with major plot holes (for instance, when characters are made stupider than they otherwise would be so they don't notice the obvious so dramatic tension can be increased). Basically, just make sure you have a good beta to help you and you should be fine. Passing the Bechdel Test (i.e. having at least two women in your story who talk to each other about something other than the men in their lives) will win you bonus points with me. Please, no slash or explicit sex.
Ballet Shoes: I loved this book when I was a child, and recently re-read it and realized I still do. I love that the girls love each other even when they don't understand each other. I love that the girls take care of each other and their family. I love that the girls go for their dreams. I love that being a mechanic/chauffeur/pilot is just as good a career choice for a girl as being a film star or a ballerina. I love that ambition is good, and rewarded, but that doesn't mean you should be a bitch about it.
Chalion series: what I love about this series is the way it brings theology to life without being preachy about it. The way theology is shown to have concrete impact on the way people act, and the way they respond to the world. It's not just gods and goddesses throwing lightning bolts around, but a truly deep spirituality that is fully integrated into the world and the characters. What I also love about the characters is that they are realistic and flawed and still manage great things despite (and sometimes because of) their flaws. What I love about Lois' works in general is the lyrical nature of her prose, the depth and breadth and weight of the way she uses words and themes and mood, though that's harder to pull off. If that's not your style of writing, I'd rather something plainly written than something overflowing with purple prose because you're not used to writing that way.
Heinlein--The Moon is a Harsh Mistress: I love the politics, and the relationship between Mike and Manny (I cry every time I read the end), and the economics of this book (TANSTAAFL!). But let's face it, Heinlein's attempts to write strong women sucked. He tried, which is more than most authors of his generation, but did not succeed. I would love to see a Wyoh who is recognizably herself, and yet made more realistic and given flesh through a deeper treatment. I would also love to see some deeper exploration of what it is to be a woman in Luna society, how that affects and is affected by economics, politics, interpersonal relations, etc.
Wonder Woman--She's Wonder Woman. What more needs to be said?
Okay, okay. I love the whole superhero shtick. Costume, secret identity, fighting evil, alter ego, the works. But I also love people who are realistic, who live in the real world. Sure, Diana can fly. What's life like for her on the ground? In the day-to-day stuff besides fighting evil, and what's it like to go from fighting evil to normal life and back again? How's it different living in Man's World than Themiscyra? Not just the big stuff or the obvious stuff, but the little things that trip you up the most. I want to see her friendships, how they affect her and how she affects her friends.