Weight training

For getting the best results out of weight training, it does not only take to know about what exercises to do,there is a compulsion to know how to do it. Most of us are ignorant to know the core details of every set. I have seen people workout in the gym just by looking at others and not knowing what they are actually doing.There is an another group of people who think they are the best and thats going to be the fact which is going to make them miss a lot.The only solution is...keep pestering your trainer, learn from him rather conducting experiments on your own. Few tend to attempt weight far greater than they can handle (take Squats for example) and limit their range of motion so that they can handle the weight; the key is to find a weight that you can use during a full range of motion. Work your way up after you understand the form. If you are unsure of the proper form for a specific piece of equipment it is a wise idea to ask the trainer working at that facility.

Shrugs

It is hard to believe that people could do this motion unsuccessfully but it happens.The shrug (to hit your traps) should be done in a direct up and down motion, not a circular motion. I have watched people "roll" their shoulder in the same manner a tire rotates.Instead you should grab the weight, lift your traps until they feel like they are pressing against the back of your head and squeeze, then lower the weight and repeat.

Deadlift

The biggest problem that I seen with this exercise is not keeping the head up. People begin looking at the floor and never look ahead.This sets up your form badly as people who look at the floor almost always tend to curl their back. You want to keep your back straight. When you look ahead it puts your whole body in a straighter position. Remember to keep your head up, and back straight

Tricep pushdown

Much like the bicep curl, the elbows are a determining factor in the success of this exercise as well. Once again, you lock your elbows to your sides and push the weight down using your triceps. You extend your arms and squeeze and then bring the weight back up, stopping when your forearms are parallel to the floor.

An important note-- If you raise your arms more than parallel you are likely to begin using momentum to push the weight back down. Plus if you raise the weight too high, you may take the pressure off your triceps and begin using your lats to bring the weight back down. You must be targeted only on constantly pressurising your targeted muscle.There are few who raisethe cable all the way to the very top of the machine, it looked like a lat pull down,until they got half way down and then started using the triceps, and then went back to the top again, I was wondering what body part they were trying to hit, but then realizedthat they probably had no idea either.

Bicep Curl

This exercise performed by everyone, is often done with poor form. When you perform this exercise incorrectly (and most exercises incorrectly for that matter) you take the bicep out of the lift and allow other body parts to help pull. This is not ideal because in order for the bicep to grow it must be hit directly and as intensely as possible. Mistakes commonly made here are swinging the body and using momentum to aid in the lift, as well as moving the elbows while curling.
To perform the barbell bicep curl correctly the shoulders should be pulled back, the elbows should be tight against the sides of the body and you should lift the weight using just the biceps. Once you allow the elbows to come off the body you are changing the angel of the lift for your biceps and more importantly you are most likely allowing your body to swing when you lift.

If you swing the weight you are using the momentum of that swing to help you lift the weight instead of just pulling with the bicep. To correct this use less weight. You should be in control of the bar at all times. You should be able to slowly lift the weight up, and slowly lower it back down. If you cannot hold the weight at any one point in the range of motion odds are it is to heavy for you to lift properly.
Remember, the elbows stay by your sides, if they are locked there, you will have a harder time swinging. A very easy solution to this problem is to use the preacher. A preacher curl is much more difficult to cheat on and does an amazing job of isolating the biceps .