For the mildly anal:
Enter or memorize transactions using the following format:
Business name [Acct #], customer service phone number, address, zip code (May require abbreviations to fit into Payee field) [Purchase Order]/Order number and description[s] go into Memo field.
This way, if any questions or problems arise, contact info is readily available in Quicken alone.
For the TRULY anal:
Scan and attach po's/invoices to each transaction ;-)