Distance is the one thing that everyone craves. However if you truly want to hit the ball farther, you have to train for it.
It will come down to a combination of fitness, flexibility, launch conditions and speed.
I believe distance in golf is acquired through fast twitch muscles, meaning it is more like a sprinter and less like a body builder.
One of the things Olympic Sprinters do to train is run down hill. They get there body used to moving faster and being able to control it.
Super Speed Golf has done a great job in creating a training system and drills that can help you learn to swing faster and eventually control it. However you have to dedicate some time to it.
Golfers should also get on a good Launch monitor. Understanding your launch conditions and spin rates can make a huge difference in how far your driver goes.
Take a lesson. The golf swing is a very athletic and coordinated movement. However, if you are not making an athletic swing you will not maximize distance. There are multiple power/speed sources in the golf swing, but most people do not utilize all of them.
Stay flexible. If you can maintain your flexibility it will allow you to make a bigger turn, increase swing length and the longer the club head has time to pick up speed the faster it will be moving at impact.