Be sure that you know the purpose of every single exercise, and why are doing it. You also need to have overall goals of your training. Remember, do not set your goals to high, weight and muscle will come over time.
Holding your breath when doing an exercise will cause your blood pressure to rise to dangerous levels. Exhale when doing the lift, and inhale between repetition. Breathe freely during pauses in workouts.
You need to work on all of your biggest muscles – chest, legs, abdominals, back, shoulders and arms. Strengthening the opposing muscle is always important like chest and upper, front shoulder and back shoulder. Letting one muscle becoming way stronger and bigger than the opposing, will cause a bad posture in many cases.
Lift an appropriate amount of weight
To give the muscle the optimal stimulus to grow, you should have to be able to at least 8 repetitions. A weight that causes fatigue after 10 repetitions is a close shot to the optimal muscle building weight.
Forget your shoes
The will keep you steady during a lift, and they will also protect your feet from falling weights.
Lift and lower the weight steadily, and try to isolate the muscle you are working on. Do not rely on momentum to able to lift as heavy weights as possible.