5 Bits of Random Leg Training Wisdom-
The biggest mistake is form. Guys go to heavy and cheat. Or do not use a good range of motion. They just want to impress other guys and girls at they gym.
Whether you train the whole leg at once or split up quads and hams depends on the person. If your hams are very bad, train them first or on another day. If your hams are pretty good, you can probably be alright training them with the quads.
Eat a little more carbs than usual before a leg workout. But not too much. Not a good idea to have a huge meal of any kind before leg training. Then you feel sick to your stomach and that ruins the workout. That is probably a reason you hear about so many guys throwing up from squats!
Never try to see how much you can squat or leg press for just one rep. Being a bodybuilder, that is just a bad idea. While a good way to get hurt as well.
Your muscles need time to recover from a workout. Bigger muscles like quads and hams need more time. Usually legs stay sore for at least two to three days after working them. They would not be recovered enough. Train legs every 5 days. Best scenario is giving them a whole week between workouts. Adding muscle building supplements help build muscle mass and muscle recovery.