My thoughts on making friends:
1) Decide to be single for a while. Focus on yourself, figure out more about who you are and use the time to be around friends, family, etc.
2) Take an interest in people. One time I had no plans on a particular night, and I was all "woe is me" because everyone else seemed to. Then I was talking to a new co-worker, and I just asked if she wanted to hang out. I thought for sure she would say no...but she looked really happy. I've learned over time that most people are too busy thinking about themselves to reach out. So when you reach out, you stand out. There are tons of people out there right now who are interesting and need another friend. Find them and make friends!
3) Find a group that is dedicated to a common interest. This is one of my favorite ways to meet people. Take a class, join a religious group, do community work. Again, there are tons of people in these places who are really interesting and also seeking friends. Who knows who you might meet?
4) Think about your interests and explore things you enjoy. If you're happy, people will flock to you. Happiness attracts friends.
5) Get outside your comfort zone. You might meet people you never would have been friends with in high school, but who can be great friends to you now. Also, you might find that you've changed. Plus, getting used to being in new and challenging situations makes you very interesting and very bold.
Just my thoughts...