"Don't force things to open, close, or go back into the sheaths."
Roger that. I have enough scars already.
If it's open, return it that way. If you want to close it, ask how. When your finished looking, put it down where you picked it up if possible, or on the makers side of the table if you both wandered. Help the maker control his inventory loss from thieves.
Put it back the way you found it. Make sure he sees it before you leave - don't be made a patsy.
Teach your kids to do the same - first rule is "No looking with your fingers!" Second rule - "No asking questions or whining when Dad's talking or looking."
Third rule - keep it entertaining for them - they can't see much on the table if its above their eyesight - and don't be long. Get them something, too.
Collect makers business cards and put them in a case, anything.
Don't point out defects unless the haggling is really close. You already decided to buy, anyway, and that just may be a character mark of hand fabrication.
If you're paying cash, have close change. It makes it easier on everybody. Small bills are usually never a problem in quantity - makers run out and can't always just leave to get change.
If yu've never worked retail, please remember that the customer always thinks he's right - but has no clue, or you would have a table on the other side of the isle. Be nice. It's not the mall.
Save questions for knives you really like. Accept the answers, they are a lot more work than they sound. Like ice skating - you weren't there at practice to see them bust their butt on the ice day after day.
Don't ask about custom changes or features unless you really have money in hand, hundreds are preferred, in bills and days waiting.