I'm new as a host, and it was important to me to get good reviews from the earliest guests so I could earn those 5 stars. I had worked hard making the house comfortable and was friendly, informative and accessible to the guests before and during their stay.
A few days before arrival, I send them local information and information on the house and using the lockbox. I live in a different town but have a reliable local person to clean and help if there's a problem. I send a message to them the day before or the day of arrival, asking them to text me after they've gotten into the house and checked to make sure everything was to their liking. Also, for them to contact me or the local person if they have any questions.
After check-out time, I always send a message to the guests thanking them for choosing my house for their stay. I ask how their stay was and to please let me know, whenever they have time, of any suggestions they have for a more enjoyable stay next time. Then I tell them that airbnb will be sending them an email asking them to review their stay. I ask them to give a "great" review within the next few days if their stay was positive.
I work hard all during the process to make my guests comfortable and informed and I don't see anything wrong with asking for a review. All 5 guests so far have been great and some have given me suggestions, which I'll definitely consider implementing. So far, I've been very pleased with my guests and I think they've been very pleased, too.