First off I agree with most everything that's been said so far. I have a couple things that I would like to add.
Really concentrate on bringing the rod to a full stop at the ends of the forward and back casts. This will help load the rod and let the line lay out flat. You can even exaggerate the pause beyond what is needed to make yourself remember.
Go get a pair of cheap sweat/wristbands. Put one on your casting wrist and tuck the rod butt under it while you practice. This will show your arm and wrist what the proper position feels like. They sell $50 gizmos in fly fishing catalogs for this, but a wristband works just as well. You can also use the cuff of a long sleeve shirt.
When I was learning, I needed to visualize the rod stopping at 12:00 on the back cast in order to make it actually stop at 2:00. Turn your head and watch the rod and line on the backcast to see what they are actually doing and then compensate accordingly.
If you can't find an experienced caster to learn from, get an instructional DVD. It's not as good, but it's miles ahead of bumbling along by yourself.
Cast at a target. Toss a frisbee or whatever out in the yard and cast to it. You can start by standing about 20 feet away and simply lifting the line, pausing at the top, and setting the line back down form there.
Lastly, as was previously stated, slow down and lay off the power for now. And don't worry about distance. That stuff will come later.
Hope this helps.