On the flip side, if I can I prefer to purchase fish straight from the bag and especially if I know who the wholesaler is. If the fish remains listless and uninterested while being handled I tend to pass on it. This is also a great time for an up close conditioning check. When window shopping, take time to notice how the fishes react to one another and reactions to you. Look for obvious signs of disease and the system as a whole. Ask the lfs if they medicate their systems or livestock (copper is common). A basic health check could be:
Obvious system water quality degradation
Dead fish in displays (also being consumed)
Obvious disease (Crypt, bacterial infections, viral infections, etc)
Physical attributes (coloration/discoloration, nutritional deficiency, breathing, etc)
Activity of livestock (physical reactions, feeding reactions, etc)