Cards are easy to sell well and easy to sell in a way that produces an argument three days later.
Putting a predicted grade in the title
Nobody can promise what a raw card will grade. A number written as a fact becomes the thing the buyer believes they bought. Say it is an opinion, or leave it out.
Photographing flat
A card lit straight on hides surface scratches and print lines. Tilt it under side light, hold it still, and show the back — centring problems usually appear there first.
Pricing raw against graded sales
Two markets, two sets of buyers, one of the most expensive errors in the category. What cards are worth.
Posting in a plain envelope
A card is ruined by one bend. Sleeve, rigid holder, taped top, bag, boards, rigid mailer — six steps and a minute. Packing cards.
Saying "mint" about a raw card
In a trade with published scales, "mint" from a seller who does not grade reads as marketing. Describe the four things graders look at instead: centring, corners, edges, surface.
Burying a good card in a bulk lot
Somebody always notices, and the story travels further than the sale.
Ignoring heat and humidity
Cards curve in a hot room and spot in a humid one, inside the sleeve. Storage is part of condition here. Monsoon and your stock.
The one that costs most
Not showing the back. It is half the card and the half that usually carries the problem.
Questions people ask
Should I grade before selling?
Only where the likely gain clearly beats the fee and the wait.
Is it worth selling commons?
In lots, yes. They fill a room.
Can I clean a card?
No. Anything you do to the surface is damage or looks like it.
More: selling cards, how they are graded.