|Regular checking of your weight is very important.|
But how often should you weigh yourself? My recommendation would be to weigh yourself at least once a week (If you can do it daily, then that would be ideal).
By weighing yourself frequently, you will notice if the weight is going up and you can then determine the root cause of the weight-gain - and hopefully, take corrective action to reverse the process.
Keep in mind that your body weight fluctuates during the day by at least 1 to 2 kilos so it is very important that you weigh yourself at similar times. For example, if you noted your weight immediately after getting up, make sure that the next time you compare your weight, you do it at the same time.
Keeping track of your weight itself is of not much use - unless you have a target goal in mind. Calculate your target weight by using a BMI calculator, and then plan your course of action (exercise, diet or both) to achieve your ideal weight. Keep track of your progress by noting the weight on a notebook. Analyze your progress and adjust your diet/workout accordingly.