The source document is pub 463. http://www.irs.gov/pub/irs-pdf/p463.pdf

You can document your meals one of two ways. either actual expenses, or you can use the standard meals rate. If you are laying over in a huge city where everything is expensive (e.g. NY), it might be better for you to take the time to look up the standard rate for NY (64$ versus a conus standard of 39$). Or, you can just go with the Transportation industry rate of 52$....again, likely the local standard rate might be higher....and if you use the transportation rate for even one trip, then that is the rate that you have to use for the entire year.

If you use the standard rate, doesn't matter how much you pay for meals.

If you elect to go with actual expenses, then you don't need a receipt if the meal is less than 75$ (page 26). What you do need is "adequate records" such as an account book, diary, statement of expense, even a computer file, or logging it in a pda. What it needs to show is the amount, date, place. And you are good to go.

And, you have to remember that whichever method you choose. You do have to report the amount your employer reimbursed you.

Other things to know, if you don't have enough tax deductions to exceed the standard deduction, may not do you any good to keep track of all the info. (one exception is for ANG/Reserve folks since the travel and per diem comes out earlier in the tax form in appreciation of your service)

If your situation is complex, look for an aviation accountant. If it is relatively simple, and you take the time to look at the tax pubs yourself, not that tough to do. I use turbo tax and have never had a problem setting it all up.

Great source for deduction ideas and have heard good things about them from other folks.
http://www.pilot-tax.com/