The photograph is never the pot you'll get.

Size — Within about a centimetre either way. Two mugs from the same day hold noticeably different amounts of tea
Colour — The same glaze fires differently depending on where it sat. The variation across one kiln load is wider than most people expect
The marks — Three small spots on the base where it stood, and often a fingerprint in the glaze. Both are meant to be there
What is consistent — The shape, the weight in the hand, and whether it pours properly. Those are the things worth being fussy about
If you need a matching set — Say so, because it is a different job — more pieces get made than you order and the odd ones go to the seconds shelf
Ordering more later — Will be close rather than identical. If exactly matching matters to you, buy the whole set at once

A glaze crawl — A bare patch where the glaze pulled away. It looks deliberate about half the time and it changes nothing about using it
A warp — A rim that isn't quite level. Only visible on a flat table with something in it, and it costs a third off
A firing mark — Where a piece touched a shelf or another pot. Always on the outside and always where you'd expect
A colour that missed — The glaze came out somewhere I didn't intend. These sell fastest, which is a running joke here
What is never a second — Anything unsafe. If a piece has a crack or a glaze fault that matters, it goes in the bin rather than at a discount
Where they are — On the shelf by the door at the studio, and occasionally online. Ask and you'll be told honestly what's wrong with each one

You won't make a nice pot — Not on day one. You'll make three, two will be bad, and one will be kept — and that is a good first session
You leave empty-handed — This is the thing nobody says. Your pots need drying, a first firing, glazing and a second firing
So they come back weeks later — Three to five, because a kiln fires when it is full rather than when it would suit anybody
You will be filthy — Clay goes everywhere. Short nails, no rings, and clothes you have stopped caring about
It is harder than it looks — And also more fun than it looks. Both of those are true and only the first one is ever mentioned
The course is the real thing — Six weeks, because the second week is when it starts making sense. A taster is a taste rather than a lesson

Clay I don't know — Is a no. Clay fired above its range turns to liquid and takes the kiln shelf, the elements and everything else in with it
That isn't caution — It is a four-figure repair and a month with no kiln. Every potter who has done it once never offers again
Clay that came from here — Is a yes. $8 a piece for a bisque and glaze firing, and it goes in with the next load
Bringing your own glaze — Also no, for the same reason. The studio glazes are here and there are eleven of them
If you're set up at home — And want a firing, ask anyway — sometimes the clay is identifiable and the answer changes
What I'd suggest instead — The community kiln two towns over takes outside work and knows how to test it. They get named rather than hinted at