Years of talk at a counter can leave a buyer with a different understanding of the contract than the paper gives. What goes wrong is usually a gap between what was said and what was signed, and that gap is easier to see early than late.
What the gap looks like
The seller describes a repair as always included, but the contract lists different parts. The seller calls a term standard without showing it on the page. The seller asks for payment before the full contract is in your hands. Each of these is a reason to stop and ask.
Recognise the pressure
A deadline that exists only at the counter, a special offer that ends if you read first, or a request to sign before a copy is printed all push a buyer past the reading step. Ask for the full contract, and ask for time to read it before you pay. A company that is clear about its terms can wait for your reading.
Write down what you were told
Keep a short written note with the date, the seller's job title if one is given, and the words that matter, such as the parts named or the claim route described. Do not write down a quote you cannot check. Then match the note to the contract and mark each point that is not on the page.
Test the cancellation route
Read how a contract is cancelled, whether any part of the payment comes back, and who must receive the written request. Ask the seller to show these on the page. If the answer is only spoken, it is not yet part of the deal.
For how the exclusion and listed-parts wording differ, read the comparison of the two styles before you sign anything you were only told about.