Exercising definitely makes me feel good, it keeps up my metabolism and relieves stress. I've also discovered that eating healthy is just as, if not more effective at keeping my energy level high and fatigue/laziness low. I use a lot of healthy eating tips from Men's Health books and the magazine. There are too many diet plans out there. But a lot of people fail to realize you don't need to go on a diet, you can eat as much as you want as long as you're eating the right foods. I've never been overweight, though in the past I've not had proper eating habits. I read a lot about nutrition in the "Abs Diet" book series. Even though 'diet' is in the title it really just explains the healthy natural foods that you should eat a lot of, and why processed/fast-foods are so bad for you. The most basic rule for a food is you should be able to trace it to something natural (eggs, lean meat, fruits/veggies, low-fat dairy, whole-grain wheats)
As for exercising, I lift weights at least 3X a week with just-cardio days 2X a week. A strong core (abs, lower back) is critical in really any sport out there, because it provides stabilization and balance. To increase your metabolism it is wise to KEEP EATING throughout the day, small meals in between breakfast/lunch/dinner. You can never eat too many veggies/fruits, they are great snacks, so are simple things like natural trail mix with nuts and dried fruits. And drink a lot of water, often times you can mistake thirst for hunger.