I have a fairly set lifting routine. I have a five day routine, each day focuses on different muscle groups.
Day 1 - Chest and Triceps
Day 2 - Back and Biceps
Day 3 - Shoulders
Day 4 - Arms and Abs (Core)
Day 5 - Legs

I really should do core every day, but I just don't like spending more than an hour to an hour in a half at the gym.
Also, I try to change up the actual workouts for each muscle group every couple months. It is working out fairly well so far. Though I really feel like I should add some cardio to my routine. And I don't take any health supplements or protein. I work out to feel good about myself, not to get big or ripped.