Welcome aboard...

Here's the 'Top 10' tips;

1- Make sure your hosting configuration is correct ( folder/file permissions, allow_url_fopen, etc..)
2- Keep a log of all changes and mod additions you add to your site (definitely any core file changes)
3- Always backup a file, if you are adding core changes.
4- Always do a full site and database backup when upgrading site to a newer version
5- When purchasing mods, check version compatibility before purchasing (ask mod developer if you are see more unsure of compatibility)
6- When purchasing mods, make sure you follow install instruction very carefully. Post issues in mod developers support forum (if available)
7- Search the forums for issues and tips. Many issues and/or tips have been answered many times
8- When making changes to files on your site, delete caches (via ftp) [Do NOT Delete the .htaccess files in cache folders], to insure correct display
9- When posting in forums, make sure you post in correct area/section. Be patient when posting questions.
10- Good luck with your site and Enjoy!!

Good luck with your site!!