I'd switch off in work out days, and in actual work outs.
For example, one day you might do..
Bench Press
Abs
Bench Press
Abs
Bench Press
Abs
etc... do rotations, and try to do abs in between just about everything. It'll hurt like no other, but it works out pretty good. When you've done a set of bench presses, don't just sit there. If your abs are too sore, work out something else.
You gotta work on your core to have any strength, so abs are important.
And as far as switching days, one day you should do Upper Body, the next maybe do legs, and then switch back to upper body, rinse, lather, and repeat. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
If you're really looking to beef up your muscles, look into a protein diet. Eat protein bars, protein shakes, eat a lean chicken or steak for dinner. Focus more on actual work outs, and less on cardio too. I usually did a 25 minute max on the bike or treadmill, just so I could build a bigger figure.