If your event is going to be outside, you need to be prepared to provide electricity, which means you will require a generator. Check with your catering, lighting, restroom and entertainment providers to see exactly how many amps they will need, and at what voltage. Relay this information to the generator purveyor and they will be able to recommend the proper generator for your event.
If your property is remote, and your set up will also require power, you will need to make sure that your generator has enough fuel, or that you have extra fuel on site in case the generator needs a refill. Discuss this with those vendors who will be doing any installations before the actual wedding day.
If you decide to add items like fans or heaters, due to last minute weather issues, make sure that your generator can still handle all these demands.
If you are using the inside of the home at all for the event, even if only for the caterer, or band, you should consider putting another generator on hold, lest the home lose power for some reason. Unfortunately, I have worked several events where there was a complete loss of power in the home and having a back up generator really saved the day.
Your restroom trailer will need a source of water. Usually a garden hose is a sufficient supply. If you absolutely don’t have access to a water source for the restrooms, you will have to swap out that trailer for port-a-potties.
Your caterer will also need access to water for brewing coffee, at the minimum. They should be able to get by with access to a sink inside the house. If there is no water access on the property, additional bottled water will need to be brought in to accommodate the needs of the caterer. If the property has no water supply, make sure all vendors are well aware of this.