I'm 6'0 and 185 pounds. I have very little muscle mass and would like to trim myself down to a lean look and gain some muscle--hell, a 6-pack would be nice (see below).
For the past month or so (and at least for the next 6 months), I've been lifting at my school (be aware I'm still in high school) after school for about an hour, doing fairly basic lifting regiments with some of my friends whom are in sports.

I'm aware that getting a lean look and a six-pack is a combination of diet and exercise. I'm going to try to limit what I eat while I attempt to reach my goal as well--are there any things I should avoid and what should I try to eat more of?

Also, what regiment should I use? My treadmill is very loose and I have no idea how to fix it and it's currently hovering between -10 and 20 degrees outside where I live. I'll look at how to get the treadmill fixed soon, but is there anything else I can use? Right now I'm using a fairly makeshift combination of up-downs for a minute and 50 jumping jacks, which I know is probably nowhere near what I should be doing--I'm very limited in my HIIT knowledge.

In conclusion:
(Though this is slightly off-topic) What should I avoid and what should I eat/drink more of, as far as foods go?
What is a good HIIT regiment for someone with very limited abilities (I can only run about a 7:30 mile...)?

Thanks.

Look at your diet first - or more specifically, the number of calories you're taking in. If you want to look lean, you likely need to drop some fat, and dropping fat means losing calories in some way.

This excellent article by Tom Venuto does a great job of discussing ' Calorie Calculators & Calorie Calculations ' ( including explaining & calculating your things like your BMR, " maintenance calories ", etc. etc. ) and how you can use this info to help you lose fat.

Calorie Calculations and Calorie Calculators: How Many Calories a Day Should You Eat?


This second link below ( ' Delware link ) it actually does a BMR / maintenance calorie calculation ( discussed in the article above ) for you.......

Delaware Consumer Health Information Services


To help figure out what kind of foods you should be eating and how many times a day!, this " 7 Habits " article represents a sound approach in deciding what ( and when ) to eat.

John Berardi - 7 Habits

Finally, if you want to lose fat, it's always a good idea to first get some rough idea of how much fat you currently have on you. You do this by calculating an estimate of your " body fat % " ( btw .....most ' 6 pack " abs start to show somewhere around 10% or so )

You can use this on-line calculator to ' ballpark ' your body fat %.........

BBLex - Calculator: Bodyfat calculation by US Navy formula

The idea is simply to burn calories and any cardio will help you do that in an effort to lose fat - so, you don't HAVE to do HIIT ( although HIIT is one of the more optimal approaches )

If it's too cold outside and you don't have access to any cardio equipment, you can do a home cardio workout to burn some calories. One option you might consider is do a pure " bodyweight " cardio circuit...no need for weights or cardio machines at all.

For example, this is one I used to do at home ( i.e which also has jumping jacks ) . It's about a 25/30 minute cardio workout. Between each exercise, rest for no more than 1 minute.

1. JOG IN PLACE - 4 minutes ..warm up

Start slowly and gradually increase the intensity by lifting your knees higher.

2. JUMPING JACKS - Do 50

3. ROPE SKIPPING - 90 seconds

4. STEP-UPS - 2 minutes

Step up and down on the bottom stair of a stairway, or on any step that's up to a foot high.

5. MOUNTAIN CLIMBERS - 90 seconds

Get on your hands and knees, then raise your knees like a sprinter in starting blocks. For one minute, run in place in this position, supporting your upper body with only the palms of your hands. Keep your back straight, not arched.

6. PUSH-UPS - 30 ( or your max )

7. SQUAT THRUSTS - 90 seconds

From a standing position, drop to a crouch and immediately thrust your legs straight out behind you so that you're on your toes in the push-up position. Now jump to pull your legs back to your chest, then stand up to complete the motion. Try to do 45 in 90 seconds

8. COOL-DOWN - 3 minutes ( i.e walk around )

Do this circuit of Steps # 1-# 8 ... the full circuit a minimum of 3 times ........that should get you pretty winded once you're done 3+ circuits and it'll burn a lot of calories .

Thanks a ton for the speedy + informative response.
According to the provided calculator I have an estimated 16% body fat...time to get working! :P
I'll stick to your cardio workout until it gets warmer outside, too.