The short version of how to get a GF, from my experience:
1. Meet lots of people. Far more than you think is enough. If only 1% of people show any interest in you, you need to meet 100 of them just to find one. You're not going to get by with just meeting the occasional new person at class or work. It really is a numbers game, like Sales -- you're selling yourself or the idea of dating you.
2. Get intelligent and realistic about who would be right for you. Everyone wants the perfect 10 in terms of looks, but in reality looks fade, and there needs to be a real person underneath. Also, given how in high demand that perfect 10 woman is, realistically what are your chances of landing that person? Realistically, what do you bring to the table, in personality, knowledge, experience, assets, and any other intangibles that would make you a good candidate to date? This question is easier than it sounds to answer, and not nearly as harsh as it may seem, but the point is that you really need to assess who is within your reach, and why.
3. Work on your own PR/Image. Don't be someone you're not, but everyone could stand to dress a little better and pay attention to small details that matter (like hair and teeth, or shoes matching your belt). Additionally, work on your social skills, and incorporate both positive (people being nice to you) and negative (people reacting badly to you) feedback in terms of what you work on.
4. Get a job, if you're not already employed or a student. Let's face it -- most women don't want to be the main breadwinner, and houses/children/other things are expensive -- most households need 2 incomes. If you are serious about a future with another person, be serious about your own future. There are a lot of jobs out there, some you can do from home, especially these days. You need to have an income to move forward with your life. It's really that simple.