I recently addressed this question on the WoW Forums (a guy asked for help with a girl he liked), but the thread was quickly deleted. Maybe it was the subject of dating that Blizzard didn't like or maybe (and it had better be this) it was the asinine, hey-baby answers the poor guy got.
But I did my best. And here's a cleaned-up version of what I told him.
How to Tell If She Likes You
If she's nice to you, that's always good, but remember that she might just want to be friends. (Sometimes friendliness is just friendliness.)
If she doesn't respond to (ignores) all of your attempts to find out if she likes you, she's probably avoiding the topic because she doesn't want to have to reject you, but she will if you press her.
The best way to find out is to just go ahead and ask her on a date.
How to Ask a Girl on a Date
The most important part is also the most difficult: be confident. Men are attracted to appearances, but women are attracted to attitude. And there are a few surface buffers you can put in place to help.
Appearance: No, you don't have to get a tan and go to the gym to get the right kind of biceps. Just make sure your shirt isn't wrinkled and you put deodorant on that morning. Take a shower. Be hygienic. (If you want to go the extra mile, get a haircut and wear some nicer clothes. Sounds mundane, but it usually boosts my confidence to know I'm looking my best.)
Actions: Don't look at her shoes. Don't fidget. Force your body to relax and make sure to smile at her (with your eyes and not just your mouth). Keep your gaze on her face (bridge of nose is sometimes best) and try to appear calm and collected. You want her to think that it would be a comfortable, interesting experience to date you. It's a turn-off for girls if they think "Is he going to be this nervous if I go out with him? Man, that would be stressful for me." Confidence in guys puts girls at ease and makes them more likely to say yes. It's terrible, but it's true. The less worried you are, the more likely you'll get a good experience from the whole thing.
Words: This is obviously going to be different for each girl. In general, though, just ask her casual questions and let her talk for a little bit. Everyone likes to talk about themselves, and doing so usually makes people feel like they've connected with the listener. Be honest and be sincere. (Girls can sense sincerity, and we LOVE it. Even if the girl isn't interested, she's going to try and be extra gentle letting down a sincere guy.)
You can tell her why you're interested in her (personality quirks, little things you've noticed that you like, but NEVER anything about her body or she'll think you're shallow). Oh, and make sure she knows you're asking her on a date. I've noticed that guys tend to avoid the "d" word when asking girls out (*cough* myhusband *cough*), so the girls don't know if they're actually on a date or if they're just going out as friends.
Never be negative about yourself. Girls don't like self-deprecation, and it also puts seeds in the girl's mind that "Maybe he isn't as cool as I thought he was." You want her to think well of you. (If you start going out, she'll find out your faults on her own, anyway.)
Try to make her feel at ease. Tell a joke if you want to, but tell tame jokes until you know what her sense of humor is like. I've had guys try to pick me up with jokes that are a little too vulgar for my tastes, and that's a definite "Let me away from this conversation now" moment. It also made the guys feel awkward because they could tell I was just smiling to be polite.
Never give her permission to reject you with a statement like "And if you want to say no, that's cool," because it will put the idea of rejection in her head and make her more likely to take it.
Conclusion: In the end, you want her to think through your body language and conversation that you want her to say yes, but it won't crush your soul if she says no. This will put her at ease in making her choice and will make it an amiable experience, whether she accepts or declines.
You get better at this through practice, so you just have to jump in with both feet and forgive yourself if you bumble a couple of times.
It's also inevitable, if you're actively pursuing girls, that you'll be rejected at some time or another. If you are, and if it's not because of her having a boyfriend, feel free to give her your email or phone number in case she changes her mind or just wants to chat. Be cool about it. Be nice.
The worst thing that can happen is she'll say no. The world may end for a few minutes, but it'll start back up as soon as you get that new enchanted sword you've been eyeing.
Confident v.s. Cocky
It's important to note that confidence and cockiness are two different things. Confidence is more like "We're equals, and I think we'd be good together." Cockiness is "Of course you'll say yes because I'm condescending to ask you out."
Girls salivate at the chance to reject a cocky guy. A lot of times, though, I think guys act cocky to hide how nervous they are when asking a girl out. They overcompensate to make the experience more bearable, and in doing so they make a "yes" answer about as likely as a lvl 30's survival chances one-on-one against Illidan.
Girlfriends and Warcraft
So, you have a girl who's willing to go out with you. When do you introduce your second true love to the relationship? It's obviously hard to hide the affair -- she's going to find out eventually -- and you want to make it as painless as possible.
If you're lucky enough to find a girl gamer, like my husband was, then there's no problem. Just set up a few dates at the DeadMines and take her out for pizza and strategy on the weekend.
If, however, you get a normal girl, I'd introduce Warcraft slowly. To them, it will be "that game you play" and your main goal is either to get them into it or get them not to break up with you for spending so much time with it.
For Option A, don't talk about it too much in her presence. Talk about things you both like that aren't Warcraft. Eventually, invite her over and let her make a character. (The first reason I wanted to play Warcraft was because I got to design my own character, not because of any of the actual gameplay.) Let her take it for a test run so she can see why you play so much and help her understand the terminology of all of your Warcraft anecdotes. Don't lock her out of your gaming world, but don't force her into it either.
For Option B, you're just going to have to balance girl and game. Play when she's busy, or when you don't have plans, but plans with her should always trump Warcraft plans. If you make plans for a dungeon run or a raid with your guild, and you promised you'd be there, tell her about it so she'll know you'll be busy that night. And don't be unavailable too many times in one week. Girlfriends and games both need attention, but your game won't leave you for spending too much time with your girlfriend. Girls just need more of you than the game does. And if she's the right girl for you, she'll try to understand why you spend so much time on Warcraft. As long as you don't neglect her.