To purchase from a breeder that has a good reputation, not purchase from a petstore.

Mites are a possibility with your new snake and you need to take precautions to treat them while they are still in quarantine setup (paper towel substrate, hides and water bowl only... spray paper towels with PAM- Prevent-a-mite and let dry, use treated paper towels for a couple months and watch for signs of mites like black dots with legs, soaking, etc.

Do a lot of browsing and find a morph you really like... Purchase that morph, even if it costs a little more, verses settling for an animal you don't really like just because it is cheaper. These guys live for ~20 years or more, so it pays to purchase and keep what you enjoy.

Purchase a well-started snake that is already feeding well on f/t. Ask for weights, ages, and what they're feeding on when seeking to buy. You want a well-established feeder to give you the best chance of having a good feeder at home. Preferably, one that is already taking f/t rat fuzzies, pups, etc.

Find a source and / or have a plan for getting your feeders before you get your BP. Buying online in bulk can save you a lot of $$ as can purchasing from a local breeder. Many areas don't have a local source though, so you need to investigate beforehand.