Dryglove:
As previously stated it takes a few dives to get used to diving a drysuit. There are basically two ways to dive a drysuit by using your suit for bouyancy control or adding just enough air to the suit to eliminate excessive squeeze and using your BC for buoyancy. I prefer the latter as it eliminates a lot of the feet up problems especially when in a heads down position looking under rocks and such.
This is good advice but what is essential is that you not be overweighted.
As long as you are diving with a normal sized single tank (no doubles, pony, stage, deco bottle, cannister light, etc) and are properly weighted so that you are neutral at the surface qt the end of the dive with 500 psi in the tank and as litle air as is comfortable in the suit, you will be fine using just the suit for bouyancy control and would not have to mess with the BC.
If you add any extra weight or use larger tanks with a greater swing weight, the air needed in the suit to be neutral becomes too much to control in the suit and you get that out of control or balancing on a bubble feeling. In cases where you have to take extra stuff along, carry some of the air for bouyancy in the BC. It increases task loading but is far easier to manage than having excess air in the suit.
So on your next dive focus on paring your weight to an absolute minimum to enable you to maintain neutral bouyancy with a minimum amount of air in the suit. Keep only enough air in the suit to offset most of the squeeze and if you find you are overweighted and need more bouyancy, use the BC. At the end of the dive, remove weight until you are neutral with a slightly snug fit in the suit, 500 psi in the tank, and no air in the BC. Once proper bouyancy is established, dry suit diving will be a lot less work regardless of what bouyancy management method you use.
Personally though even after 20 years in drysuits, I still prefer the lower drag of a wetsuit in the water. A neoprene drysuit has reduced the drag difference substantially and is more comfortable than a trilam in my opinion but still, when the water gets warm enough, I go back to diving wet. And contrary to popular opinion, it is ok to own both and use whichever suit is most appropriate to the conditions.