It is easy to start a fitness program with a hiss and a roar but it is also easy to fizzle out once the novelty has worn off. So, it is important to not only start strong but stay strong to help yourself stay motivated for the long haul. By making sure you are not making mistakes so you can minimize the time you spend exercising and maximize your results.
1.)Pick a quantifiable measurement for success. For example to 'lose fat' or 'get in better shape' is too broad and needs some real numbers to measure your progress. The best way is to have a body composition test (muscle/fat ratio). This will tell you how much fat you are losing and how much muscle tissue you are building or maintaining. A fitness professional at your local gym can do this for you.
2.)Too many big changes at once, because people seem to want dramatic and instant results. New exercise program, restricted calorie diet and taking up running all at the same time will only lead to failure when this high level cannot be maintained for more than a few weeks (if that long). Start slowly and add a little bit more each week is the way to go for sustainable changes in your lifestyle that will last.