Most photographers have a radius around their base location that does not have a travel fee. Outside of their radius, they might have incremental travel fees by distance which can include fuel, mileage, lodging, etc. Consider how far you are willing to travel and what your no-fee radius would be. If you anticipate that a wedding might be particularly far away, then consider incremental fee increases by distance and have that information prepared in advance. You might research wedding photographers in your area and their fees to get an idea of your regional standard.