DUDe i used to train people as a trainer and this is what i would do
First of all they look retarded trying to do a squat because its a lot going on at one time. Its like riding a bike u just gotta get used to the motion. I would place a bench behind them and just tell them to sit down because that is the motion they need to get used to. When they sit down and they know something is behind them it forces them to sit "back" and stay on their heals which is where a lot of ppl mess up. So after they get that down I put on weight, just the bar (i always trained women so the bar was kinda a lot at first)
After this I would take a video of them doing it with the bench, and then a video with them doing it without the bench. With them being able to visually see what they were doing, they corrected their problems a lot easier rather then when i was telling them what they were doing wrong.
Hope this helps brotha. Also id start with feet wider, toes pointed a little out