First your diet You have to eat well if you want to stay fit. Technically you don't want to diet; diets are temporary. What you want to do is change how you eat for good. That means no extra sugar, no extra butter and you might as well cut back on the salt, no fastfood, and no frequent visits to all you can eat buffets.
Your food is your energy and you really are what you eat. Everything you consume is used to make up a part of your body; extras are usually made into fat. So you shouldn't just eat something because you're bored and the food's there, but you shouldn't starve yourself either. Starving yourself puts your body in a mode where it will burn muscle for a fuel quicker than it will bodyfat. And plus once you finally do eat, you'll eat a lot more and your body will be more efficient at storing fat. A good way to eat correctly is to eat small portions often. That way your body is always fueled and there's no overbearing hunger. 6 small meals a day has been recommended often. And to help you stick with it you can cheat one day a week. That one day you can eat whatever you want; this helps give you something to look forward to if you are thinking about quiting.
Now exercise If you want to lose weight fast you have to burn more energy than you're used to; this will use up more fuel. Plus having more muscle will mean that at rest your body will require more energy than it did before; so you'll burn fat more efficiently. It's good to keep consistant at this, maybe workout 3 - 5 times a week. And, I've read, to really boost fat burning, exercise first thing in the morning on an empty stomach. This way you're using your fat as energy, not something you have in your stomach. If you're going to go all out and exercise for a long period of time, it might be a good idea to eat a real small snack with some carbs in it before you workout. That way you don't risk burning your muscle instead of fat. Remember what I said about the starvation; your body can naturally go without food for only so long, then it's ready for you to break the fast (breakfast). So don't over do it. There's so many different things you can do to exercise: You can run, jump rope, lift weights, run up and down stairs, box, aerobics, anything that you don't normally do will help to boost your fat loss. You can even just take a long walk if you're not used to working out and you'll see some results.
Results You see that poorly drawn bathroom scale up there? Don't pay too much attention to that. Sure you can use it as a gauge if you want, but you have to realize that muscle weighs more than fat. If you lost an amount of fat the size of your fist and you also gained an amount of muscle the size of your fist, then once you hop on that scale you're going to notice you've gained weight. Then I'm sure you'll be thinking, "Oh this workout sucks, I'm not making any results, I better quit." But in reality you're doing really good and making nice results. Also if you lost a pound of fat and gained a pound of muscle, and you hop on the scale, you haven't lost or gained any weight. Once again the question in your head, "Where are the results?" Well they're there, you're making good results, but by only using the scale you can't really notice them as much.
The most accurate way to gauge your results is to check your body fat percentage. You can use the manual and digital body fat calipers, but they're not the most accurtate. The best way to check your body fat percentage is the Hydrostatic Weighing tests they have at colleges and such, but those can be pricey. I think the best way to know if you're making results is to look in the mirror. How do you look? How do you feel? How do your clothes fit? Take before and after photos. Are people complimenting you on how good you look? That's the best and cheapest way to know if what you're doing is working.
Now go out and try these things Research this topic more on the links I have, and enjoy your body. EAS has lots of supplements and tons of tips you can use. Men's Health is a good magazine I read from time to time. And Charles Staley's site is chock full of ideas and products, he even has a free newsletter you can have emailed to you.
Men's Health Site
Charles Staley's Site
Other Sites to look at