You can do squats more efficiently. Make sure you lower the bar down at the center point of the traps. This will put a lot higher demand on your hamstrings, hips and glutes, which allows you to lift more.
Make sure you understand the best exercises to increase muscle mass. Different exercises work on different parts of the body, and can either build muscle mass or tone your muscles. If your goal is to build muscle, then you need to know which exercises can help you reach that goal faster. Combine the use of weight machines with free weight exercises for a more effective muscle building routine. Because free weights have more movement to control, they can add mass quicker. Beginners will often feel more comfortable with weight machines, as form is less of an issue and injuries are less likely. If you are new to muscle building, include both so that you do not get stuck on only weight machines forever out of habit.