2 Day
Body Split In Half - Lower Body On Day 1, Upper On Day 2.

This, to my mind, does not make much sense despite the fact it's a common split. The problem here is on day 1, you do legs. On day 2, you have to do everything else - that's back, chest, deltoids, triceps and biceps.
Don't forgot to include trap, forearm and ab work! So, how can you possibly train all these muscles with enough intensity to generate growth? You can't! Of course, you can change the body part groupings and do less sets and see some results.

Here's an example:

Day 1 - Legs, back, biceps, forearms, abs
Day 2 - Chest, deltoids, triceps, abs.
This type of routine usually revolves around basic exercises. It's usually performed over 4 days - Mon/Thurs for workout 1 and Tues/Fri for workout 2, allowing 3 days of recovery. Of course, you can do it however you like, taking days off anywhere in the split as needed. Those of you who read my stuff know I don't always stick to a 7 day workout week, if need be, I go to a 8 or 9 day workout week.

Also, a routine of this type - with each workout done once a week - is often suggested as a great hard gainer routine because of the recovery time. Limit the sets, perhaps do no direct arm work ( eliminate arms from the above and you can see you have a much simpler routine) or a low set total for arms and work the basics hard.


3 Day
Push/Pull Routine

Day 1 - Legs, abs
Day 2 - Chest, deltoids, triceps, abs
Day 3 - Back, biceps, forearms, abs.
This is a very common split routine - it makes a lot of sense as well.


Day 1, you do legs by themselves, which, if you squat (and you should) makes sense since leg work, done properly, is so grueling.

Day 2, you do the pushing muscles - this makes sense as deltoids and triceps are involved in all chest exercises and triceps are involved in all deltoid exercises.

Day 3 is pull day - this makes sense as biceps and forearms are involved in all back exercises. While some people do this complete split twice in one week ( 3 on/1 off), for many of us, once a week makes more sense.
This can be done on a rotating schedule where you always allow 2 days between each workout or on a set schedule where you train on pre determined days every week, such as Sunday, Wednesday and Friday.

Yet even this routine can pose problems - you may be to tired to give deltoids, triceps, biceps and forearms any real intensity.


4 Day Split

This routine allows further dividing of body parts than the push/pull split listed above:

Day 1- Legs, abs,
Day 2- Chest, triceps, abs
Day 3- Back, biceps, forearms
Day 4- Deltoids, abs
This allows you to group a smaller body part with a larger one, or just train some of the bigger areas alone, this way you can train all muscles with more intensity. While some advanced bodybuilders will do this a 4 on/ 1 off (1 day off out of 5) routine, you can squeeze in recovery days any way you like to or need to. As if you can't guess, I would definitely add more rest days to this.


The One Body Part Per Workout Split

You can set up rest days any way you want. Many people who use this use it as an "every other day "split or will even train 6 -7 days in a row. You can divide up muscles any way you like, including sub-dividing: back into upper, lower and lats, deltoids into front, middle and rear, etc.
This is not a very popular split but may be good for pre-contest and/or for someone with a lot of time.


The 6 Day Split
Arnold's split routine, really a 3 day split done twice in one week, with only one rest day.

The Double Split

This is actually Arnold's pre-contest routine: twice a day workouts, 6 days a week.

The Triple Split

An even more advanced pre contest routine where you train 3 times a day, usually a big body part such as legs in the morning, maybe cardio in the afternoon and a small area like abs at night, usually including posing practice at that time as well.

Conclusion

As you can see, there are a lot of choices. Many of these are advanced and are meant for people with a lot of time . The 3 day push/pull routine typically can meet most bodybuilders needs. I favor this one myself although I have used a 4 day split set up to train deltoids ( as listed above) on their own day.

I set this up over 8-9 days to allow for good recovery. This also allows extra work on weak body parts, and allows you to train for complete development. I don't use it now because my schedule has changed and it is no longer practical.

The most important thing to remember in using any split routine is to set it up to give you good recovery. Do that, eat good and train hard, which will force you to keep your set totals reasonable, and you'll make progress.