GREAT thread!
I'm at the point in my diving where I'm in serious jeapardy of developing bad habits. I've been certified since August, and have completed 60 dives. I worked really hard during the first 25 or so dives to focus on my basic skills, but after that I have to admit to a bit of complacency -- spending more of my mental energy just enjoying the dive, and not giving quite so much thought to all the important stuff I need to be thinking about to be a solid, safe diver.
And then I had a couple of minor incidents that could have gone the wrong way...and I realized that I'd kind of forgotten some of the stuff that I learned in my OW and AOW classes that I don't use on every dive -- especially emergency measures. So now I'm back to mixing in some skills & drills dives along with just-for-fun dives.
It's too easy to forget the things we don't use on every dive. But we sure don't want to realize we've forgotten them at the moment we truly NEED them!
Oh, and I have to echo the thing about using your hands. That's something that my experienced dive buddies harrassed me about to no end at the beginning, and I worked hard on learning to keep my hands quiet. I recently went to a diving resort where I saw lots of divers, and I realized I could pick out the inexperienced divers from the experienced ones in a heartbeat -- the new divers were waving their hands all over the place, while the experienced ones mostly kept their hands or arms clasped beneath them. It's hard to accept at first that you really don't need to move your hands in the water, and that they are pretty ineffective anyway in terms of moving you...it's just something that takes some work.