There are a number of common mistakes people make when trying to burn fat, lose weight and gain muscle:

Isolating exercises like bicep curls and tricep kick-backs will not get you any significant results. These one-muscle-at-a-time moves simply don't stimulate enough muscle fibers to build lean muscle or expend enough energy to maximize your calorie burn. If you want to build lean muscle while burning fat so you can get serious definition, you need to perform exercises that stimulate as many muscles and expend as much energy as possible at the same time.

Fancy machines may make the gym look high-end, but truthfully, about the only thing they're good for is for sitting down while you tie your shoes or catch your breath! The problem is this: Machines alter the way your body naturally moves and restricts your range of motion. This severely limits your ability to fully activate all of your muscles fibers and that means less fat burning and less muscle definition. Worse yet, machines can cause excessive strain on your joints, leading to nagging injuries down the road.If you want fast results, it's critical that you incorporate exercises that allow your body to move naturally with full range of motion so you can skyrocket your metabolism and tone your entire physique. 

Cardiovascular exercise is an important part of any weight lose and burn fat burning routine but there's a right way and a wrong way to incorporate it into your workouts. If you've been pounding the pavement or the treadmill with nothing to show for it you already know it takes a lot of effort to get minimal results. Replacing long cardiovascular routines with higher intensity, shorter duration burst will yield far better results and faster. 

If you want washboard abs, doing traditional abdominal exercises like crunches and sit-ups will not get you a six pack. Remember that isolated exercises don't do much and that's exactly what a sit-up is, therefore doing them is a complete waste of time. The key to getting sculpted abs is to burn off that stubborn layer of belly fat that's hiding your abs and that means working hard on everything and eating right.

Repeating the same workouts over and over is a surefire way to stop getting results. We're creatures of habit and we tend to stick to things we're familiar with and good at. But when it comes to your workouts, if you want to keep making progress and keep seeing changes in your body, you've got to start switching things up. It's called muscle confusion. You see, your body has an amazingly ability to adapt quickly and when it does, that's when you hit the dreaded plateau and you stop making progress.