Each month, we fill these pages with fitness and nutrition “must dos” to educate you and keep you on the right track, but sometimes the best way to develop good habits is by learning what not to do.

If you’re looking to shed some bodyfat, there are some very basic guidelines anyone can follow to start achieving results. For some reason, however, there are still those who make a few cardinal mistakes. Here we explain the IO things you absolutely should not do if you want to get lean. If you’re doing any of them, your physique is in big trouble. Now go to you room and read.

“Heavy weight just bulks you up,” says the shapeless gym enthusiast. “Lighter weights with higher reps is what really gets you ripped.” Tsk, tsk tsk. Mr. Nonsense and his amoebic physique have good intentions, but this way of thinking is as archaic as eight-track cassettes.

High-rep sets definitely have their place–increasing muscular endurance and pump, for instance–but they should never from the backbone of your program when you’re trying to get lean. Sticking to lightweight sets (12-20 reps) for an extended period robs you muscles of what they need most–a constant challenge. In the absence of new stimuli, such as constantly increasing weight loads, your muscles will simply grow content and either plateau or backtrack in size and shape. Lifting heavier will help you gain more lean tissue, which allows you to be slightly more metabolic at rest. Plus, heavy training (6-8 reps) increases the total caloric expenditure during and after your workout.

BEST TIP: Base you program on heavy, multi joint lifts such as squats, deadlifts and various presses that recruit and build more total muscle and burn more calories. Use moderate (10-12 reps) and lightweight (12-20 reps) sets to complement your heavy training, not the other way around.

Performing cardio before weight training

Some silly folks like to shamelessly exploit a fundamental training mantra–that you should always train for priorities. If losing bodyfat is your primary goal, for example, then cardio should be your primary focus in the gym, right? This is one case where your priorities are just backward, pal. While cardio by itself is certainly productive, doing cardio after your weight-training session is almost twice as productive at burning fat.

Japanese researchers recently determined that doing a weight workout before cardio resulted in significantly more fat-burning than doing cardio alone. In the study, a cardio-only group burned just more than 20% of their total calories from fat, while another group who did cardio after weights burned nearly 50% of their total calories from fat. One reason for this amazing disparity is that the body plows through stored glycogen during your weight routine, making fat the primary fuel source once it’s time for your cardio.

BEST TIP: Perform cardio when it’ll be most productive for you–after you hit the weights. Try mixing in 3-4, 20-30- minute, postlifting cardio sessions per week.

Eating fast-digesting carbs preworkout

Before you hit the gym, you definitely want to have some protein, but some people still reach for white toast, Gatorade and other fast-digesting carbs to round out their preworkout meal. Somewhere on a cave wall it is written in ancient Sanskrit: A crab is a carb is a carb. Today, we know better.

Your definitely don’t want to head to the gym on an empty tank, which is why you should fuel up in the 60-90 minutes or so before your first rep. But before you guzzle a sports drink or have a baked potato, know this: Fast-digesting carbs will have a negative impact on your body’s ability to burn fat for fuel in the gym because they boost insulin. This anabolic hormone is great to boost after the workout for encouraging muscle growth, but during the workout it blunts fat-burning.

BEST TIP: While having some carbs in your system is ideal preworkout, you’ll want to make smarter choices to keep your fat-burning high. Take in 30-40 grams of slower-digesting sources such as oatmeal, whole-grain bread, fruit or sweet potatoes 15-30 minutes before training. Research shows that athletes who eat these foods burn more fat.

Always doing steady-state cardio at 70%-80% of max heart rate (MHR)

We love those skinny dudes who hit the treadmill with a heart-mate monitor strapped around their chests–it helps round out their already stylish headband-and-Adidas Gazalles look. But that leisurely prance is simply no match for a hard-sweat, fat nuking interval session

Steady-state cardio done at 70%-80% of your max heart rate will definitely eat away at bodyfat, but you may be selling yourself short. Your best bet is to train using intervals, where you frequently alternate between bouts of high intensity (80%-90% MHR) and low intensity (50%-60% MHR). This method of training leaves the body burning more fat long after you put in you last sprint–no heart rate monitor required.