I will soon be traveling for my job on a contract for a federal government agency. What do I need to have in order to receive federal government per diem rates at hotels/motels?

Usually a work ID showing that you work for the federal government is sufficient. Or a letter stating that you are on federal govt business with your state driver's license?

You can call the hotel and ask, when in doubt, but those two methods should work.

Normally when I worked for the government the hotels needed to see my government ID. Other than that they would want to know the agency I worked for and their contact info.

As a contractor, you are not actually an employee of the government, you work for a company that has a contract with the government.

If you are traveling on federal govt business (but not an actual employee of federal govt), some hotels may still give you the per diem rate (for example, if you will be reimbursed by federal govt).

Same if you are traveling on state government business and want to get the per diem rate.

It depends on the hotel, so call ahead and ask.