Let the customer know that these are animals you bred (not just some misc. merch. picked up wholesale). Give info on feeding, last shed, etc. You can offer to send a copy of the snake's records (date of hatch, feeding schedule, weights, etc.) home with the snake. Show pics of the parents and discuss how you expect the baby will develop.
Are you in any way, attempting to gently "close" the sale? Don't let your customer just stand around indecisively holding the snake you know they want. Even a slightly awkward close that you might feel uncomfortable making at this time (ex: "Would you like me to ring this one up for you?"), is better than nothing. The customer may need to look around some more. You might offer to hold the animal back for them for an hour or two. You can also use this predicament to assist them in finding what they want. Be helpful - maybe you know Joe across the aisle has some nice examples of that morph. Tell the customer you will be around until such-and-such a time if they should decide to go with one of yours.
Just some random thoughts.
Never vended at a reptile show.