Ask on the listing before the show where you can — the answer stays there for the next buyer, and sellers answer public questions with more care.
The questions
"Which parallel is it?" The same photograph exists in many versions at very different scarcities, and the parallel is frequently the entire value. Non-answer: the player's name again.
"Can you show the back?" Centring reads there, and so does staining.
"Can you tilt it under side light?" Print lines and surface scratches live at an angle.
"What do you think is wrong with it?" Specific answers are the mark of somebody who has looked.
For slabs: "Which service, what grade, and is the case intact?" Grades are not interchangeable between services, and a cracked slab is damage.
For a valuable raw card: "Can you measure it?" Modern cards are a standard size, so a trimmed card measures short. A seller with a good card loses nothing by showing it.
About predicted grades
An opinion, not a comparable. Never pay a graded price for a raw card on the strength of one. What cards are worth.
What protection covers
Damage not described, a different card than shown, a slab misdescribed: seven days from delivery.
Questions people ask
Why do the same numbers mean different things?
Different companies, different standards, different market reputations. Ask which.
Is a bulk lot worth asking about?
Ask for the sport, the era and the condition range, and whether anything notable is in it.
Can I ask for it out of the toploader?
Yes, and expect some sellers to decline for valuable cards.