I am sure there will be plenty of articles online about preparing your Mac for the Mojave OS. This article describes things you should consider and do before upgrading. It is pretty thorough, but has good information. I have been running the Mojave Beta’s without too many problems so I think I will upgrade right a way, but YMMV so proceed with caution. Of course, good backups and a clone of your Mac would be ideal before proceeding.