Most important rule: keep contact!
Nothing more raging indeed for a contributor than not receiving any news once a campaign has ended.
Best practice n°1: a thank you email during the hours following your campaign with the coming milestones.
Best practice n°2: share the advancement of the project. You have a prototype, you start the recording at the studio or started preparing the rewards? Share it with your contributors to show the project is ongoing.
This behavior is essential if there is an important delay between the end of the campaign and the delivery of the rewards.
Remember to spoil your contributors with exclusive pictures and announcements. Your project is getting real thanks to them, and it’s another way of showing gratitude.
Best practice n°3: transparency! An issue, something unexpected or a delay longer than expected? Talk about it! Your contributors believed in you and want your project to take place, keep them in the loop and explain why they need to wait.