As a noob, I:
-only used default builds
-was using desktop controls and didn't know there was laptop controls so I wanted to buy a number pad
-once i figured out laptop controls, built spammy crap
-didn't know how to talk
-paint everything rainbow and undulo
-put add-ons in the wrong folder (the folder in Program files and not the bl file in documents)
-didn't build with baseplates
-didn't know about forums except the add-ons area
-a bunch of other stuff