I ran into this problem, and I found that finding people to do stuff with is a good place to start.

I treated it like an RPG and leveled up my social skills. For instance, you can find people on http://www.meetup.com/ You can do community events to meet new people and interact with them. I also recommend reading (or in my case listen to) http://en.wikipedia.org/wiki/How_to_Win_Friends_and_Influenc...

You can also date people by a number of ways, and I recommend craigslist (where I met my fiance). If you go this route, then you will need the stamina to go through 1000s of ads and tens of disappointments, but there are many options. (I didn't want to pay any money, and I figured my significant other wouldn't want to spend money either.)

The key to it is: Don't give up.