I've heard lots of folks badmouth running, saying it'll destroy your ankles and knees. I've also read lots of studies that show it's one of the most productive activities you can do for your health, and it doesn't cost anything. I believe, if you're overweight you'd benefit best by walking off the weight, or using cardio machines. A weight training regime to sculpt fat-burning, lean muscle mass will also be invaluable, and the third part of the equation is a balanced nutrition plan. Even after you've gotten your bodyfat percentage into the 20-25% range, it's a good idea to stick to the Cardio, Weight-training, and Balanced Nutrition Plan.
When you begin a new running program, start slow, and listen to your body. Light stretching before and after can be helpful. Proper form is very important. Pay attention to your posture while running, and let your foot strike beneath you rather than in front. That will save your joints and shins some wear and tear. Visualizing and mindset can also be helpful. The way I like to look at it, is I try to concentrate on those seconds where neither of my feet are touching the ground. Those moments where I'm literally airborne are a lot of fun. It's my favorite part of running.