1: If possible offer your guests to be picked up from the airport. It adds that much needed personal touch.
2: Ask for their preferred cuisine and check if they would like you to order a take-out of their favorite meal. (And a double check for allergies if possible)
3: Plants and a bit of nature is loved by one and all. Indoor plants and soothing water fountains count too.
4: Being clear and setting your rules is less stress for you as well as the renter.
5: Is inviting guests okay or not?
6: Will there be any extra charges for additional guests/members?
7: Have emergency phone numbers emailed to them.
8: Make sure you are not being too rigid. After all, it is a service you are providing and being customer friendly is the first rule one must follow.