You must be traveling far enough away from home that an overnight stay (or more) is reasonable or required, and the travel must be temporary (lasting less than 1 year).
You can deduct 50% of your actual food expenses provable with receipts, or 50% of the federal per diem for meals and entertainment. (In Turbotax, enter your actual cost or the per diem and turbotax will calculate the 50%.)
The federal rate varies by locality and you can look it up online. The rate for travel days (the start and end of your trip) are reduced.
