One of the best tips I can give anyone is find a sport you love. If you have to force yourself to "work out" or "go to the gym" you won't stick with it, but if you find something you love to do just for fun then you'll want to do it more and more. Doesn't matter what it is - rock climbing, tennis, wrestling, rock climbing, raquetball, soccer. As long as it involves sweating a lot and you grow to love it and want to do it every week for the rest of your life it'll have a great impact on your fitness.
Now diet is 80% of losing weight but if you are playing a sport you love you'll discover the weight comes off faster when you're eating right and it comes on slower when you're eating bad. Finally, you'll also find you want to eat more healthy because as you make bad decisions and gain weight you'll find it hurts your athleticism in your sport or if you find yourself going out and drinking you'll find the hangover hurts your sports the next day and you won't want to have those consequences anymore. So you'll find yourself wanting to make better decisions.