How to start losing weight healthy and safely, w/o buying otc pills and such... ?

I have had the worst time losing weight, and at one time I exercised faithfully for over 2 months, and I maybe only lost 5 pounds... I want to get back into exercising, but I dont want to wear myself out trying to do it. Are there any suggestions on how to get back in the mode, and start gaining more energy again to start successfully losing weight?I am a terrible planner, and usually jump in it full force, to where I wear out and then just lose interest...