Hard work.
Find a sport you like, and supplement it with activities you dislike...for me, that's doing squats, or time runs. Ugh, I suck at running, but I can pack on muscle like it's my JOB.
And take the time to look through a Sports Illustrated, and realize that there are so many world-class atheletes out there who don't have the Adonis body-type, but they're good at what they do.
I recommend that you pick up a book like this:
Frances Sienkiewicz Sizer, Eleanor Noss Whitney
Nutrition - Concepts and Controversies (with CD-ROM, Dietary Reference Intakes Supplement, and InfoTrac)
http://www.wadsworth.com/cgi-wadswor...ssn=0534090524
Above is the book's website.
Once you buy this text, it's a good start for understanding basic nutrition. It does go over the benefits of exercise in a general sense, but is invaluable for the DIET ANALYSIS software.
If you are really serious about nutrition, (as you
must be) then you can use the diet analysis software to get HARD DATA on your daily diet, and how it matches with your Recommended Dietary Intakes, the food guide pyramid (which is currently being totally changed by the FDA) and overall calorie needs. If you read the book, you'll learn that you may need more or less (generally more for young, active males) calories than 2,000 per day.
You need a plan, and a methodology, and more than anything, a way to get support. find some friends, find a nutritionist or a personal trainer to meet with every couple of months, to monitor progress. Numbers can be your best friend, in your situation.
Good luck, and stay motivated!