I think this is something hard to put down in words but,,,, here goes.
First hands on lessons are needed for someone to look at the mechanics of your swing. Hitting the long ball to most people is not just a matter of strength, it is a matter of proper technique. The biggest problem I see is players trying to hit the ball too hard. A well hit ball just "feels" right. We have all seen young kids and players who are not that strong who just have a "natural" or well trained swing and hit a nice ball. Yes there are big guys who also hit the heck out of the ball. NEVER get between Tommy Biddle and where that ball is going
There are plenty of videos that will help you with the idea of a good swing. Tom Goodspeed has a very good series of tips and videos. http://www.polobarn.com/goodspeed/goodspeed.html
Watch good players and their positions thru the swing. The extension and smoothness of the swing. How they follow thru with the swing.
If you can have someone video you from the front AND side. watch the arch of your swing. the plane of the swing should not waver, think of it as a pendulum. Control is more important at this point than power when learning.