As a seller and buyer on eBay, I have noticed a few things from some users that need to be addressed when selling or buying figures.
Figures should not be erroneously listed as Mint if they are in fact not. They should especially not be listed as Mint in Box, MIB, Mint on Card or MOC if they are not. Mint means it is in perfect condition, never played with, never really even displayed, preferrably never removed from the wires that hold it in the plastic. Mint in Box (Mint on Card) means the box or container has NEVER been opened, not for a peek, not to play with once, just NEVER. Any figure that is not in these conditions should not be listed as such. This information should be NOWHERE in the title of you auction at all. Additionally, this information should be present in the body of your listing. It should state exactly what the buyer is getting so there is no confusion. It is best to give the MOST information rather that forcing buyers to send you messages to find out about you listing. This will encourage more users to look at your item.
Custom Figures should be listed as such. Regular figures by the manufacturer that have had no modifications should not have CUSTOM in their title. Don't falsely represent your figure.
Shipping for a single figure should not be multiple times the cost the buyer is paying. Raising your shipping costs or using rediculous cost shipping is not a way to get your money back or "stick-it" to the buyer. It should NEVER cost 3-4-5 times the cost of one figure to ship it. e.x.: shipping for a $2 figure should not be $10 if it is nationally shipped.
These are just as few guides that should be used by all users.