Shame Young_Warrior just got banned
It's definitely a good habit to pick up on, I've been going on and off for years, and pretty consistantly since April or May. If you're looking for an aerobic workout (treadmills, etc.) then I suggest getting out of the gym and just running outside.
If you're planning on lifting, the gym is great. If you're like me and are really lazy, I suggest getting a friend to pick up the habit with you, it makes it much harder to blow off because somebody else is waiting to go with you.
Schedule?
3 days a week is probably a good schedule to start off at, just make sure you have days of rest in between (go on Monday, Wednesday, and Friday or something)
Routines: I don't have time to explain every one but a quick internet search should show you what part of the body each exercise works, and explain how to do it.
If you're looking to work your upper body good exercises to start with are:
Benchpress, Crunches, Bicep Curls, Tricep Pulldowns, Military Press, Pullups, Push ups... just try to incorporate every muscle group, most machines will tell you what muscles they work. (chest, upper back, lower back, shoulders, biceps, triceps, forearms, abs)
I don't know too much lower body, I rarely lift with my lower body, but squats and calf raises are good to do.
As far as how much to do 3 sets of 10 is a good number to work with for most exercises.
Remember to eat enough protein before and after you lift, it'll help a lot if you're trying to build muscle.
Good luck, as you can see I'm no expert and I pretty much just do my own thing at the gym, but I hope I could still help.