Which fields in an opportunity drive assignment?

The following fields drive opportunity assignment: Account, Sales Channel, Product, and Partner (for assigning partner-centric territories).

Other, peripheral, account and partner attributes also drive assignment, but aren't captured or displayed in the opportunity. Examples of these other attributes include: Primary Address (Geography), Named/Not Named (Account Type), Industry, Organization Type, Partner Type, Organization/Customer Size, and the Auxiliary 1-3 Classifications.