POF

When doing reps the amount you do should always be to POF which is point of failure.  I usually do 3 sets of an exercise with the weight set so im getting about 15 reps before POF on the first set.  Really push yourself!  When you think its all you've got, push for just one more rep and than ones more.  Really motivate yourself to the point where you can someone holding a gun to your head and saying "give me one more rep or ill shoot you."  Imagine that every time you feel like quitting until you really cant do anymore and you have to quit halfway through your rep and congratulations you have reached Point Of Failure!  Go to POF every set and you are sure to get a good workout worth being proud of.