How to get a girlfriend? How to make her your girlfriend? While I can't solve this issue in one article, I'll give the best starting point that I can for it.
It is both easier and harder to make a woman into your girlfriend than it is to date her casually. Because monogamous relationships are the dominant relationship type in our society, women will often assume that this is where your relationship is going unless either of you say or do something to imply otherwise.
This may seem strange on the surface. After all, you probably have not ended up in Traditional Relationships with most of the people you've slept with. This is because people often "say or do something to imply otherwise." This can be very subtle. For example, if she mentions other men or dates at any point after the first hour or so of your interaction, she's probably not looking for a Traditional Relationship. If you have a "party" vibe about you and never seem to get serious, she may assume the same about you.
Now, let's assume that you do want a Traditional Relationship. How to make her your girlfriend?
The good news is that a lot of this process is not all that different from getting her to sleep with you - show enough interest to get her looking in that direction, but not so much that you come across as pushy, clingy, or not a challenge.
In other words: get close to her without being clingy.
Your goal is to see her two to three times per week and for her to come to the conclusion on her own that she doesn't want to see other men and/or that she'd rather give up the ability to see other men in return for knowing that you won't see other women. It's important for her to come to this conclusion herself as opposed to your pressuring her.
If you pressure her into a commitment before she feels completely ready - or at least ready enough to bring it up or hint strongly at it herself - then you're significantly adding to the likelihood that she'll cheat on you later. So let's not do that.
For best results, start when in Comfort. Vague long-term plans based on common interests are a great idea. For example, if I'm dating a woman who tells me she loves art, I'll talk about how we have to go to the Getty Museum one day. If we realize we both love ice hockey, I'll comment on how we have to go to a game. If she wants to be a better cook, then I'll suggest we take a cooking class at the place under the Arclight, and maybe make it more specific by agreeing on what kind of cuisine we should learn.
[For more information, check out Chapter 9: Comfort in Magic Bullets.]
Not only are you uncovering great date ideas, but you are also 1) reinforcing any emotions she has that you and her have some exciting possibilities ahead, 2) communicating that you see potential for some kind of longer-term relationship with her, and 3) helping her imagine herself with you in other contexts in the future. Don't actually plan anything at this stage - keep it vague. Planning is boring for many women and takes away excitement and adventure and can make everything feel "too serious" to her.
Right after you first sleep with her is a key time. Solidify the connection if you can. Stay over or invite her to stay over. Have breakfast together. Call her the next day. Communicate to her by your actions (without saying it) that she's not a one-night stand to you. That's easy enough. Now do all of that without being clingy. There's no formula here. You're just going to have to use your intuition.
Also remember that women can be very unpredictable right after sex, so she may display emotions that actually have nothing to do with you. Don't react to these. Society (both the media and her peer group) bombards her with messages that her worth is tied up in her sex appeal but also makes women feel guilty or cheap for enjoying their sexuality. If she's got some odd emotions to deal with, the last thing she needs is some guy being needy. She may well act very distant from you, but still like you a great deal.
Call the next day. Handling this call correctly is crucially important. It must not be awkward.
Don't refer to having had sex with her. Don't call to "check in" with her. Call because something funny happened that you want to tell her about. Be the same natural, fun, and interesting person you were before you slept with her. Don't let any awkward silence develop, but don't sound nervous or talk too much or too quickly. If you're worried about awkward silences, cue up enough topical things to talk about for at least an eight to ten minute conversation. Don't rush into making plans unless she seems very warm and comfortable to you on this call. End the call first.
On one of your next calls, invite her to do something. If she sees you again after you've slept together, you're well on your way. Use each time you see each other to discuss mutual interests and upcoming events. Further dates will follow naturally out of these conversations. For example, say you are both talking about your love for classical music. You mention that you have tickets to the symphony for next Friday. Presto. You have another date.
At some point, she should give off some indications that she's committing to you. For example, she might reserve part of her weekend for you, or want to know what you're doing on the weekend so she can make her plans. She might suggest a weekend getaway. Introducing you to her friends more than once is a very good sign. Listen to how she introduces you, and make sure to invite her along when you are doing some activities with your friends, especially exciting high-status activities. Remember, women lose social value if their friends perceive them as easy, so if she's introducing you to them more than once, she is probably not introducing other men at the same time.
If she hasn't given any of these signals, be patient. Use the telephone to your advantage. A couple of phone calls during the week, each ideally ten minutes or so, to tell her about something interesting that happened or to check in on something specific in her life (if she was sick before, to find out if she's feeling better, if she just started a new job, to find out how that went) works wonders. It shows that you care and that you listen. Most of the usual telephone rules still apply.
At some point, she will bring up the idea of you as her boyfriend or ask you if you're seeing other women. This is not a time for a jealousy plotline. Just be genuine here. Your goal is very close.
It is a rare woman who will see you two to three times per week and never refer to you as her boyfriend or initiate a discussion about the future. But if it happens, then the responsibility falls on you to say something like "I feel funny bringing this up, but I realized we never actually talked about this. Are we supposed to be seeing other people?" Be emotionally neutral - and not nervous - when you say this. One way or another, this will resolve the issue.