My advice is for after your course, not during. When you solo dive, there is no buddy to look you over and ask about things. There may be no one in the water to help address an oversight after-the-fact. Since over the years I've managed to variously jump in with air not turned on, even once hit the water without fins, and since I've left a pair of expensive fins on a dive boat when I headed back to catch a cruise ship, I do a little regimented check list before I splash, and sometimes before I exit the boat (replacement fins cost money).
1.) Mask (touch it).
2.) Regulator (touch it).
3.) BCD (touch it).
4.) Boots (point at them).
5.) Fins (point at them).
6.) Dive computer 1 (touch).
7.) Dive computer 2 (touch).
8.) Camera (touch).
9.) Air is on (take small breath off regulator; check that low pressure inflator hose is connected - inject a little air so I see BCD bladder gets gas (in Bonaire where gear may be stripped down in the evening for a rinse, it's easy to forget to hook it back up).
10.) If all is good, make an 'Okay' sign with right hand and nod. Ritualized process and confirmation is important.
Because laziness, distractibility and taking things for granted are inherent to the human condition for me, do the above preferably 3 times before hitting the water. Don't gloss over the process like 'yeah, yeah, yeah' - focus on it. Also, get in the habit of securing your tank cam bands tightly (you likely already do).
A diligent, methodical process you ingrain in yourself is key preparation.
And I'm not particularly anal retentive or that diligent by nature.
