my dad rides his bike to work every day and my mom is a nurse/nutritionist. Because of so my family is pretty healthy. Nonetheless Ive found that aiming for 1500 calories a day, no matter how you get them, tends to be all you need to maintain a generally healthy weight, so long as you get a *little* exercise every week (preferably cardio).
A great way to keep the pounds off Ive found is actually to drink lots of fruit juices instead of sodas and avoid large meals that you can put off (not hungry right now? Don't eat). Also, small forms of exercise like simple manual labor jobs like prexus mentioned are good. Parking your car farther away and walking, or riding a bike places are also good. Get in as much exercise as you can, or at least want to, and avoid any excessive eating. Additionally, drinking plenty of water at meals never hurt either.
Thats the simplest way to keep a healthy weight. Ive been stuck at 112 lbs for the past three months as a 15 yr old 5'2" sophomore. I'm skinny as fuck and in terms of muscles I can bench a good... 50lbs. It might be slightly different for some of you, but what I just described is my way of keeping a healthy weight.
Edit: also, if you need some caffeine every morning, go for some coffee with sugar. avoid Sodas as best you can, but if posed with the choice of regular or diet soda, take the regular. Diet sodas are for diabetics who can't have sugar, and they can simply wreck whatever diet your on. Unless you're diabetic or are avoiding sugars, avoid diet sodas. better yet, don't drink soda at all.