They’re alert & active - may be cheeping softly, looking for food & will move away from you when approached. Chicks that aren’t well will appear lethargic & constantly sleepy & may not try to move away when approached.
If chicks are happy, healthy & warm, they won’thuddle together when awake.
Bright-eyed - chicks with a blank stare, crusted eyes or always sleepy may not be healthy.
Look for a beak that is not crossed over or broken- birds with beak issues will have problems eating & drinking.
Healthy feathers - unless you’re buying an older chicken during molt, chickens & chicks shouldn’t be missing feathers.
Straight legs, feet & toes - an unhealthy chick may have difficulty walking or have poor posture with its neck retracted into its body.
If a bird is acting dull, withdrawn or hunched over, it could indicate a serious problem.