Mites, what to look for before buying?

I'm a new guy here but it seems like there's a ton of threads of people buying snakes with mites. What are some simple prepurchase snake buying tips to avoid this situation? Years ago when I first owned snakes I'd only buy from venders that had snakes displayed on white paper towel, I'd look hard at everything they had for that little black dot. I'm sure there's better mite spotting methods

mites tend to make the scales stand up slightly when they burrow under them, so if you pick the snake up and manipulate their body so they make a bend crawling through your hands, it exaggerates the scale standing upon the outside of the bend giving you a view to where mites hide. Mites however are normally easily spotted. What isn't spotted is mite eggs. Thats why many of use make it a practice to treat all new snakes like they have mites and pretreat the cage with mite spray. Even if eggs hatch, you will already be fighting them. Also quarantine will prevent mites from becoming an outbreak, in the event they do hatch.

An easy check is to take a roll of white paper towels and a spray bottle of water with you. Mist a paper towel with water and wipe the snake with it - it's easiest to just let the snake crawl through the paper towel in your hands. Chances are if the snake has mites, at least one should end up on the paper towel.