Knowing what is actually on sale verse what’s not. Amazon has a large tendency to hike up prices right before Black Friday so the “sale” is really just it going back to a normal price.
Also don’t buy certain things like TVS that are on a big Black Friday sale. It’s not the same TV. It’s a cheaper quality.
Many companies cheaply mass produce products just for Black Friday.
I honestly don’t shop it anyone because I’ve noticed the price trends and low quality of things. I try to buy stuff earlier on for Christmas and such now.