The biggest problems I see at the range with new shooters are mostly safty related.
1. Not keeping the finger off the trigger when not shooting. Most times while walking to, and from the shooting area.
2. Not locking the weapon open, or opening the cylinder while walking to, and from the firing line.
As far as shooting form.
1. Not leaning forward enough to keep the gun from pushing them around. Most times they are leaning too far back.
2. Flinching (Many new shooters that follow basic advice do great for the first couple of shots. Then after the loud bang catches up to them, they shake, and flinch.
3. Limp wristing. I have seen this happen a whole lot.
No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.