If you have luggage to carry along, then you have to inform the driver in advance about how much luggage you have. Otherwise he might not be able to take the luggage along - which would be very bad for you.
If you carry pets along, then you have to get permission from the driver in advance. Some people are allergic to pets like cats and dog. It can be even life threatening for them. So tell him about your pets beforehand and get permission!
Clarify where you will exactly meet. Tell the driver how you look like. Ask him how you can identify him! You and him should upload a profile picture so you can easily recognize each other on the day the ride takes place.
Ask the driver what else you have to consider. It's important to communicate well and plenty with each other - then nothing will go wrong! The more questions, the better.