If you're gonna lift twice a day, IMO it's a good idea to train EOD, and train two or more muscle groups every workout. Which means you won't do as many sets each workout for each muscle group, but instead you will hit each muscle group more frequently.
Ideally, you'd train the whole body in one day. Either split half of it in the morning, and the rest in the evening, or a full body workout but fewer sets both AM/PM.
YIP
Zack