Ok, I need some help. I am wanting to do an upper/lower body split workout. Two days a week upper body, two days a week lower body. These are my questions:

1. If I do this, do I do the same exercises both days or do I change them up?
2. Also, it seems like if I do 3 exercises for chest, back, shoulders, triceps, biceps, forearms, etc., I would be there forever. For those that do this, how many exercises do you do for each?
3. For legs, there are multiple exercises for multiple muscle groups that I want to hit. I feel in order to do this, I need to do a different work out for each day of legs...is this what you do? Does this defeat the purpose of trying to get the muscle groups worked twice a week?

If anyone can answer these questions, I would really appreciate it. I really want to tweak my routine but need some answers first. Thanks...