A trick for standing exercises is to bend your legs slightly, taking pressure off your lower back, and stagger your feet to create more balance. As the weight gets farther from your body during the movement, you will need more force to overcome its relative weight. You need good balance and control.
One of the biggest mistakes lifters make is to start the movement by launching the bar or dumbbell with momentum. Creating momentum at the waist causes the lifter to lean back, moving the tension from the biceps to other muscle groups. Lifters often cheat at biceps exercises when it gets most difficult, usually at the 90-degree angle. However, working through that sticking point will truly enhance overall improvement in the biceps. The desire to cheat by launching the weight with momentum is natural, but the best results will come if you force yourself to work harder when it gets harder.
Developing the biceps takes time and patience. Don’t give up on them. Any pulling exercise will work these muscles. If you are having a difficult time developing these muscles, try isolating your arm muscles by inserting an arm-only day into your training program once a week. No single exercise can effectively target a specific area of the biceps, so your keys to success are performing a variety of exercises and using a full range of motion.
Another good tip is to get a spotter to assist you. Don’t be afraid to get some help. Instead of using momentum and cheating through the tough areas, get a buddy to help you a little, and force your body to remain upright during the lift. To really work your biceps, try 10 reps with a heavy weight, forcing the last few reps.