The key is to stay in communication with your guests throughout the entire stay, not just after they check out. Tell them candidly that you’re striving for a 5-star stay and ask them how their stay is going, if they need anything, and if everything is up to their standards. This gives you a chance to solve any issues before they show up in a review.
The best time to contact guests about leaving a review (and to tell them that you’d appreciate 5 stars) is on the last day of their stay, before they check out. Once check-out is complete, Airbnb will automatically prompt them to leave a review and a star rating.