I used to be pretty fat and unfit 5 years ago when I decided to make a change, I'm not a champion body builder or anything now but I'm 30 and getting fitter every month.
Here's what's worked for me:
Get an allotment (do they have them in the US?).
Spend the winter digging it over, 1 hour a day (burns about 800 calories per hour of heavy digging will have it ready for planting season.
Then grow vegetables on it. Nothing tastes better than food you've grown/raised yourself. Eat healthy as a result.
Digging ditches is the original old skool way to build muscle.
On the food front, if I'm trying to get my diet on track, I follow three simple rules - only eat things that are full of micronutrients (vitamins, minerals fibre etc), only eat wholegrains (no white bread, pasta etc), and don't eat ANY ready meals / processed food. By the time you've been "living well" like this for a while, you wont want to go back to junk cos you'll realise it tastes like shit.
That means I eat as much fish, meat, vegetables, cheese, nuts, fruit, milk as I want. Also dark chocolate if I want something sweet, and red wine. Combined with physical activity (in my case small amounts of running, yoga and gardening) it means I keep in good shape.
When I decided to get in shape, I just focused on building muscle to start off with. I figured if I could get my lean body mass up, my body would start burning more calories. I've always believed in short workouts focused on the "big three" lifts, squat, deadlift and bench. They all work masses of muscle groups together, burning the most energy and building the most muscle. Ifyou're new to a gym it's best to get some intstruction on those from someone who knows how to do them safely.
I used to weight train a lot, but found getting to the gym a real hassle. I also started to get niggles in my lower back/sacroiliac joint. When I have a little more room in my house I'll probably set up a squat rack and bench again, as I love squats.
The jury's out on caffeine. A lot of bodybuilders's swear by it. Some studies say it's a good thing, some say it messes with your sugar/insulin metabolism in a bad way. Personally I tend not to have more than 2-3 cups in day, and I try to avoid red bull, as fresh coffee has all the other good phytochemicals in as well as the caffeine.