Join some hobby clubs, its a good way of meeting people. If you have a job or you are going to college, invite someone there out shopping or something. Say you are going anyways and you need a companion and thought it would be nice if it was them.
Or even just compliment someone in a shop (your own age of course) and get to know them a little. Go get something to eat together and arrange to meet up again.
Making friends should be easy, don't force it