Nailing down your budget should be the first thing you check off of your to-do list! Decide how much money you're willing to spend before you choose a theme or pick a venue. Your budget will ultimately determine the rest of your plans.
Generally, the more people who attend the rehearsal dinner, the larger your budget will need to be, so keep the size of your guest list in mind. The guest list can be as big or as small as you wish, but it should at least include your immediate family, the bride's immediate family, members of the wedding party and anyone else who's part of the wedding rehearsal, including the officiant. You can invite extended family members and out-of-town guests if you wish for a larger group, but keep the guest list even between members of your family and the bride's. You're the hostess, but the bride and groom are the guests of honor!