How to lose 20 pounds? ?

Hi! So I'm not really overweight but I could stand to drop a few to be a bit healthier, which is really what we all want, right? :) Anyoo... I'm not really sure how to go about losing weight. I've been maintaining my weight for a few years by just doing some random cardio and eating fairly well, but I do have a taste for junk food occasionally and don't tend to maintain a very consistent regimen with exercise. Does anyone have any advice as to how I could do some things to lose weight in my spare time? At this point I'm kind of willing to do anything, although it doesn't have to be super quick. I just want to start making good choices now so I don't have to worry so much later. :) Thanks bunches!