The main thing is to follow the Canadian Food Guide recommendations. If you're eating as much fresh fruits and vegetables and as little protein as they suggest, you're already doing your body a favour! Also, try to limit what you're drinking to real fruit juices, water and 1% or skim milk. Try to cut out as much caffeine and excessive sugar as you can! Try to drink about 8 glasses of water a day
Next, exercise. I know, that's the scariest word out there. I myself get really bad shin splints when I run so that limits my cardio options. However, if you can get 20 minutes of additional exercise (especially cardio) into your daily schedule, that's great!
If you don't have a gym membership or just don't like working out in front of people, just put on some great music with a good beat, lock yourself in your room and dance like an idiot. Seriously, it's embarrassing how much I get into it. But, I sweat so much while I do it, and I feel awesome afterwards! Also, try to help out around the house... vacuuming is a great way to add a little more jump to your exercise! It doesn't have to be scary!
I also like to do a quick bit of yoga first thing in the morning. It gets your blood flowing and puts you in a good mood for the day. Here's the video I've been using lately:
Good Luck! :)