Consult with your faculty research mentor about your budget BEFORE you submit an application for funding. Do your research about costs so that your estimates are as accurate as possible -- there are multiple online resources that can help with this. For example:
Room and board for research trips: there are government websites that provide estimates for cities within the US as well as overseas. Keep in mind that these are estimates for government employees traveling for business purposes, and the cost of student research travel should be significantly less.
Travel by car: the IRS website includes standard mileage rates. Note that the business rate is for employees traveling for business purposes, and undergraduates traveling for research purposes should use the "medical moving" rate in estimating travel costs.
Compensation for research participants: the Finance Center's website has important information and guidelines. Be sure to also consult with your faculty mentor and academic department/program (and CPHS, if appropriate) for information about compensation policies and amounts.
On campus room and board: if you are applying for a leave term grant for on-campus research, you may apply for the maximum award amount and do not need to submit an itemized budget. Note that this does NOT apply to honors thesis grant applicants as on-campus room and board are not eligible expenses for honors thesis grants.