The two big factors are number of riders and distance. Let the charter company price it out for you and see what they recommend. Keep in mind that the cost of additional shuttle service can add up fast.
The bus has always stayed with us on out of state trips. We provide the driver a room. The cost of the drivers meals should be included in the cost of the charter. A lot of restaurants will feed bus drivers for free if he brings in a bus load. Ask the driver, he will be your best source of information.
Make sure everything is spelled out in the contract.
FYI Cheapest is not always the best. The story of the trip from CT to Rochester in March 2005 for Finger Lakes Regional will someday be made into a musical.
