How can I make new friends, without seeming pushy or weird?

I have a lot of acquaintances, especially at work, but I don't have a lot of friends that I hang out with socially. I would really like to change this! I am a friendly person who likes to talk to people, and I am an attentive listener. But how do you jump from co-worker/acquaintance to friend? I feel awkward asking a co-worker, "Hey you want to hang out sometime?" Not sure what to do, please any advice would be appreciated!!