Olympic style weight training will fill out your frame all-around. Few things are as effective at working muscles all-around.
Stuff like running wont help.
Over the past few months, I've had to cut out my gym membership. I can't afford it, and my car to get there has gone kaput. Terrible loss. Improving my physical health was a massive priority for me over the past year, and although I've tried, I tend to fail at doing it on my own. I need a scheduled event, like a class, to keep me from slacking.
However, in un-characteristic defiance of my usual laziness, I've been doing push-ups every day over the winter. It has been making a surprisingly big visual difference, and I'm steadily increasing the amount I can do before I gotta stop.