Weight training, like every form of exercise requires some kind of discipline, and determination. But if you have neither, the New York Times suggests that there is one exercise everyone should work into their daily routine and that is squats.
Stuart Phillips at McMaster University in Ontario explains why the squat is the one weight training exercise everyone should do:
I do think, from top to bottom, that the squat is an exercise that engages every single major muscle group... It's about as functional as you're going to get in terms of training you for activities like picking things up and standing up.
Squats help you accomplish your day-to-day activities. And you can pretty much do them, anywhere!