jbd:
....snip....
Make small adjustments and then give them time to work.
.
Just to further this, you might be asking yourself
"how much time is enough?"
To answer this question you need to think about your breathing as well as the air in your bcd. Ideally your breathing and your buoyancy adjustments are in synch. Getting it in synch takes a little practice but the basic idea is that NORMAL buoyancy fluctuates. You constantly sink and float a little. When you breathe in you start to go up a little so you exhale, which makes you start to sink a little so you inhale and so on. With a little practice you'll be able to do this without sinking or floating so much that you need to adjust your bcd all time. Also, it's very important that you breathe constantly, deeply and (especially) exhale fully so you don't build up extra CO2 in your system. In other words don't start breathing shallowly becuase it screws up your buoyancy.
But I digress.
Getting back to the topic of how long you need to wait to see what effect a particular ajustment made....and with the breathing in and out thing in the back of your mind, it should be obvious that when you add air to your bcd you really need to do two things:
1) make small adjustments, which is what jbd already said. Also, small adjustments means REALLY small. Press and let go of the button almost instantly. If it wasn't enough then you can always press the button twice. Same goes for venting.
2) then breathe in and out and wait for the results.
For example, if you added air because you were sinking then add a short burst and breathe in too. If you then stop sinking and/or even start to slowly go back up again with air in your lungs then you've found the sweet spot and you're done.
Likewise, if you're venting air because you're floating then vent a little air and breathe out too. Once you breathe back in again then you'll see if you need to vent more. Rembmer, at all times, the sweet spot in buoyancy is an approximation. You need to get it more or less right with your bcd and then do the rest by getting your breathing in synch.
One last thing about this. If you find that you need to keep your lungs quite full to avoid sinking or quite empty to avoid floating then you can make a small adjustment to your bcd to get the sweet spot more in the middle of a normal breath.
Bit of a rambling post. I hope it's not confusing. If you're taking a PADI course you'll hear all this again during lesson #3.
R..
