I have found that in order to make friends and acquaintances you have to partake in a particular organization or activity and participate on a regular basis.
I have made friends and acquaintances through my activities in the local Democratic Party, my membership at the local UU church, and through other volunteer opportunities.
Strangely, I made my closest friends through work. This does depend on the work environment, some places are more condusive to friendships than others. Opportunities for intimacy and interpersonal contact in the workplace is what fosters this.
I guess I have a problem with making friends that are my own age. Most of the people that I have met through activities have been older than me. But I have been often told that once you get older, age doesn't matter in friendships. One of my closest friends in a 80 year old retired psychologist, we attend the same church and deeply enjoy classical music and the arts.
Lastly, remember that friendship does take time, it is something that doesn't happen overnight.