FORM FORM FORM!
Many beginners get stuck on the theatrical aspects of lifting weights. They want big muscles to show off so they pound on the weights straining their backs until it cracks. Or they decide I'm just going to tone up so 10 lbs 95 reps should be good.
No matter how heavy you go, no matter how fast you lift, and no matter how often you go to the gym; improper form will lead to a proper injury.
If you don't know the proper form of an exercise, research it. Even if you have been doing an exercise for a while and havent got the results you expected still do your research. Learning proper form could help you correct your stance, correct any uncomfortable experiences, and help you target with the best range possible.
If you have to lessen your weight to correct your form do so because when you see that guy walk past you who's been out of the gym for a while. ..you'll be glad you did.