I was a freshman in college. I had done some weight training in high school, but I wasn't very informed on what I was doing. I did, however, see some small gains from my very flawed program. I think I did something like a full body workout every other day. However, not long after, I hit my first plateau. Naturally, I thought that if some working out was good, then more would be better. Soon I was doing a three hour workout every other day. I performed just about every exercise I knew. Not surprisingly, I didn't make any progress and probably got a little weaker from being so overtrained. Fortunately, I played a club sport, and one of the athletes on the team was a graduate student that had played division I football. Lucky for me, he was willing to help me with my workout program. He made two major changes:
Drastically reduce the amount of volume. Good-bye three hour workouts—I was in the gym an hour at most
Perform compound exercises with forced reps. That means that after I went to failure and could not physically lift the weight one more time, I'd have a spotter help me with a few more repetitions.
Compared to what I was used to, the results were amazing. First of all, despite the fact that I had previously been doing long workouts, I was never terribly sore the next day. After my first workout on the new program, that changed in a hurry—putting my mind at ease because I was worried that I was not doing enough volume to get good hypertrophy. More importantly, I made fantastic gains and was very pleased with the results.
So what can you do to learn from my mistakes?
Don't spend all day in the gym. If you are there more than an hour, you are probably being counter productive, as your testosterone levels may start to dip.
Get the most out of your sets. If you've been lifting for a few months and your just starting to hit your first plateau, try forced reps to see if you can create a little more hypertrophy.