Eat good regularly(5 med sized meals a day), lift on a regular schedule 4 days a week at least, find a good partner that will push you and that will spot you, an injury will wipe out months of hard work. I like to change my exercises so I'm not doing the same routine over and over and when you hit a plateau take a week off let your muscles rest. I also try to use free weights as much as possible and stay off of the machines if I can.