In the past I have had buoyancy issues, I would always swim with my arms and just deplete my tank in no time. Since then I have figured out how to keep off the bottom by adding a little to my BCD at a time, sink easily by comfortably exhaling until I start to sink, reduce the cold shock by dunking my head real good and hanging out up top before submerging, and improving my swimming with the help of the split fins.
My only issue with buoyancy is how much weight to use when I use different wet suits. I find noting how much you used with what exposure protection after a successful dive a useful tool. It saves you the trouble of remembering!