some of it depends on what you are selling and how much you're asking

if you know you're asking below market value, then as far as i'm concerned, it's a free-for-all, "get it out of my house and you win" type thing

if it's something at/slightly above CL market value, i'll try to give buyers a better "experience" since they are paying for it

By all means make rules for yourself that you think are fair and honest and stick to them.

Being upright, honest, & forthright is a good thing in this world and people will tend to respect you for it.

NEVER EVER assume or expect everyone else to following these exact same rules -even should be. Everyone has their own ideas of the "correct" way to do things. Assume no rules at all except for those written down and signed in front of a notary. Even then, have a lawyer on speed-dial if you expect them to be followed to the letter.