The quickest way to make friends imo is to share stressful scenarios with someone. The stress removes many of the social boundaries that get in the way of bonding with strangers. Think how quickly you made friends at school in your first week.
I'd suggest amateur dramatics, adventure holidays, swinging (!), evening college, book clubs, debate societies, political campaigning, charity event fundraising / participation, school boards, volunteer community projects, hiking / outdoor pursuits, sports teams (volleyball is excellent) etc. In short doing something a bit risky , something that gets the pulse racing with other people and you'll make wonderful acquaintances and then from there some true friends.