You can take the specific per diem rate for each local but you must be able to show it in a log format. If you are only doing North America, you are proably wasting your time for meer pennies unless you employer doesn't pay per diem at all.
There is a program out there called Pro Diem that will do the calculations for you if you enter the layover info. The beautiful part is it splits days in 1/4 and help maximizae you deduction. It increased my per diem expense by $6000 but then again all my flying is international to expen$ive cities.