Know the difference between coated and uncoated stock.
Coated is gloss or dull and uncoated is the kind letterhead is made of.
Know the difference between Cover and Text weight paper.
Cover weight is what business cards are on and text is what letterhead is on.
Inks/Colors you want to print. 4-color process (CMYK) or PMS colors.
This information is important to the pricing for any project. Ask if you are not sure.
Proof approval is the final step before any job is printed.
Take extra time to proof and make any changes that are needed.
Always check phone numbers, addresses, spellings of names and headlines to be correct. These items are where most mistakes occur and are so simple to check and fix.
If your project requires any extra special steps, fast turn delivery and/or packaging make sure that is very clear to the customer service person.