I'll admit it. I filled the tub with water, got my mask, and practiced breathing through the snorkel and taking the mask on and off when I got my first certification. Does anyone else do this?
I practiced the equipment exchange in my pool. By myself (kinda). I had my gear on without a tank. Hubby handed the reg back and forth (taking breaths) from outside the pool. I traded masks and bc's with him while I was underwater.
I practice hovering while students are on the platform waiting for their turn with the instructor.
I practiced the 15 minute tread in a pool 4 feet deep - talk about hard! Gotta kick sideways!
I also practice holding my breath incase I ever have any desire to do any free diving (which seems kinda silly to me when you got a tank handy).
I'll never forget the anxiety my mom had when I told her about the equipment exchange. I thought she was going to hyperventilate. She stated, "Well at least he (hubby) is going to be with you." It turns out he wasn't, but that is a whole other story.
Practice. It helps me. Repetition helps me. Knowing what I have to do helps me. Scuba is a sport of planning. I love it.