Cam, when choosing a baby BP it's more about trusting the source than anything, especially if you are buying online and having the snake shipped in. Other than that, when you are examining a snake in hand you want to do a good all over quick health check from head to tail tip....

- clear, bright eyes with no stuck caps & no denting in (may be hazy if snake is actively in a shed cycle)
- labial pits and nostrils clear of shed and dried discharge
- mouth clean, no discharge, bubbling, red/sore areas, etc. (glottis should also be clear and not mucked up)
- breath sounds clear with no clicks, pops or wheezing
- overall the snake should feel firm and athletic, not skinny with the spine showing nor sluggish and limp
- scales should be shiny, flat, no scarring, no external parasites, no brownish or pink/red discoloration on the belly (other than a faint pink if again the snake is in a shed cycle)
- vent should be clean and dry
- let the snake run through your hand to feel for bumps on the spine or broken ribs
- when turned on to it's back the snake should be able to right itself easily
- the snake may be in a ball and that's quite normal (so is being a bit strikey if it's a hatchling)
- a slight pinch on the lower 1/3 of the body (on the side) should result in the skin immediately springing back tight to the body, if not then the snake is dehydrated somewhat (practice this on the back of your own hand)
- bp's are considering a fairly girthy snake so it should feel heavy for size and not be overly triangular in body shape when viewed from above

Hope that helped.