The local lumberyard I used to support would just hand me whatever they felt like giving out, probably saving the good lumber for their big project customers. They’d also tell me things like pressure treated 2x3s don’t exist. I get much better products now from the big boxes. Menard’s has its issues but works for me (and has those non-existent 2x3s).

Big box has wood, that's true... But any serious wood working person will need a jointer, a planer, and possibly a kiln in order to use house brand wood... Find a sawyer or vendor OTHER than a big box!

Non of these tips will result in success if you go to big box stores LOL! - Support your local Lumber Yard!