How do YOU just start talking to people? What do you talk about?

So the one piece of advice that I see being given all the time is that to meet people you just have to go up to them and start talking. Now for socially awkward people like me (26M), this sounds like it would be uncomfortable to be on the receiving end.

So how do all of you go about it? How do you start and maintain a conversation with someone you know nothing about? And how do you not come across as creepy?