CliftonGK1

An easy way to assure you're using the correct muscles is to s l o w. w a y. d o w n. when lifting. The program that I use to monitor and schedule my lifting has very specific methods spelled out for a "good" lift.

4 seconds 'down'
4 seconds 'up'
2 seconds 'rest'

Now, depending on the lift, 'down' and 'up' are different, but you get the gist of it: 8 seconds for the motion phase of the lift, and 2 seconds of rest between reps.
Initially, you start out with determining your 1 rep max.
Then you back off to 65% and determine your time max. (start a stopwatch, and do 4-4-2 reps until you can't anymore.)
Muscle groups are worked in rotating sequence such that no group is repeated in a single week.
Lift weight is increased 5 pounds each time the group is worked and max time is reached. Fail to reach max time, weight is kept steady for another week.
When weight for reps = 90% of one time max, start the cycle again with re-testing for one time max.