I think a lot of people aren't as informed as they could be about how to go about their diet and workout routine to get the results they want. Its like modding a car, if you do it wrong you'll have crappy results, so research can help a lot.
www.bodybuilding.com is an excellent resource for any type of person looking for any type of fitness... and covers both diet and exercise. Your new homework is to spend at least a 15 minutes a day there browsing around reading all of the articles that interest you and the forum too.
I ate whatever I wanted as much as I wanted and always weighed between 160 and 165 lbs. I've now gotten a lot more serious about both diet and exercise as they are both essential to see improvement, and I've seen some noticeable results in a short period of time. I'd definitely encourage you guys who are looking to do this to make sure to take the time to read and educate yourself in order to make progress. And there is no shortcut or easy way with this, you will get out of it what you put into it... so expect to work for your results and feel very rewarded about where you've come.