Pretty hard to identify them but here are some steps to avoid them. The main thing to check for is whether they have certificates from your national kennel club and how often do they have litters. If they have one female dog and litters from her quite often that’s a bad sign.
Another quick tip is to avoid “designer” breeds altogether like poodle mixes and such. Way higher risk of terrible breeding practices in these cases. If you want a mix go adopt one, buying a puppy from a breeder should only really be done for purebreds.
God I hate this Nazi kibol so much. Fuck Poland for electing him.