Always ask for proof of liability insurance. A qualified and professional carriage company will always be happy to provide you with a copy. Once you have the copy don't forget to call and make sure the insurance is current and has not been dropped. You might be surprised how often fly by night operators slide under the radar on important things like experience and insurance. Its always worth asking about.
Make sure you understand how the company will deal with manure or urine should it be produced by the horse(s). You should never be left with the duty of cleaning up after the carriage companies horse. Either the use of a diaper bag aka manure catcher ( part of the harness) or someone with the company that is delegated to shovel duty. Make sure you ask so there are not any unpleasant surprises left behind.
We would strongly advise you to ask a carriage service hired to be on your property how many people will be with the horse and carriage. The answer ideally should be two per carriage. A header or footman ( person to stand at the horses head and assist the carriage driver) and of course the carriage driver as well. The driver should remain on the carriage seat throughout the event and if for any reason must leave the carriage seat the header or footman should be in full control of the horse in the drivers absence.
Pay attention to the turnout as it reflects on you also. Is the horse and carriage clean? Is the driver and footman appropriately dressed or are they shabby and in street clothes? You do not want to see a poor turnout at your venue being shared across social media platforms. It is bad for business
Do not excuse an operator walking away from his/her carriage horse while hooked to the carriage while on your property. Do not excuse the loading of passengers unless the driver is seated and has the horses reins in their hands. Do not be afraid to ask a carriage operator to leave your premises if they can not uphold basic safety protocol or it appears their horse(s) are out of control.
Never question a carriage operators wisdom about what is or isnt safe to attempt with a horse. Sometimes clients have unrealistic and unsafe ideas they pressure the carriage operator to perform. Nobody should ever ask to sit on top of a carriage horse hooked to a carriage for a picture or any other reason, and that is just one example. If the driver says no to your client always back the carriage driver up.