Thought i would offer what has worked for me.
Over the last 15 years - i have tried many different routines, ect. What seems to work for me, my build, and goals are the following: Note, it is a FLEXIBLE regimen - i work a FT job and have two boys to raise so flexibilty is key to me sticking to my workouts and thus - long term success. My regimen fits my schedule - not vice versa - helps me to stick to it.
Day 1 Chest/Biceps
Day 2 Back/Triceps
Day 3 Aerobic
Day 4 Legs/Shoulders
Day 5 Aerobic
Day 6 Chest/Biceps
Day 7 Aerobic OR take the day off OR pick up with Back/Triceps - all depends on my body - as described below.
This way, i tend to work the same body part about once every 5-7 days.
I try to avoid working chest/legs on consecutive days only because it takes alot of energy and strength.
I ONLY work-out for 30-40 minutes - tops.
I do not socialize during my workouts - it is a real distraction and messes up my goal of allowing only 2-3 minutes between sets.
I throw in ABS about once every 5 days and do nothing specific for my forearms or calfs.
I never work muscles groups on more than two consecutive days.
I take about 5-7 days "off" about once every two months.
I change my "routine or movements" about once very two months.
I "listen" to my body - it tells me when it is time to change a routine, take a day off, or to back off on the weight.
My eating habits are essential - eat too much fat and i am sluggish - drink too much alcohol and i tend to gain weight and loose strength.
I always drink a protein milk shake BEFORE the workout - for me, it helps to have the energy stores before working out rather than taking it AFTERwards.
I never do more than 30 minutes of aerobic activity (raquet ball, jogging, treadmill, stationary stuff)and try to mix this stuff up.
About three months ago i began doing something that added a little variety and does not seem to of had a negative impact. Before, i use to complete my ALL chest routines before moving on to Biceps NOW i will alternate. For example, i complete 8 reps of bench press - move over to complete 8 reps of barbell bicep curls - go back to bench press - go back to biceps - i rest about 2 minutes before each movement.
This takes alot more energy and stamina.
My 2 cents.