Vent: Painting over glossy trim without sanding first is a sure way to mess up.
I see folks try to rush through it, but paint just slides right off smooth surfaces. Had to redo my whole hallway after a botched job, and now I sand every time, no exceptions.
That point about paint sliding off smooth surfaces is SO true. It shows a bigger thing where skipping the simple prep work can ruin any project, like not measuring twice before cutting wood. The extra minute you spend early on stops a huge mess later.