wire & breaker size
Also, keep in mind that it's often a good idea to install 20 amp circuits in some situations in which a 15 amp circuit is allowed, a very typical situation I see is a "McMansion" type property with a 15 amp circuit running to a "guest" bedroom at the other end of the house from the panel, into which somebody then attempts to plug a plasma TV,a home theater sound system, a floor lamp or two, a computer - and then attempts to fire up the treadmill.
Home Inspection: ""A business with illogically high liability, slim profit margins and limited economies of scale. An incredibly diverse, multi-disciplined consulting service, delivered under difficult in-field circumstances, before a hostile audience in an impossibly short time frame, requiring the production of an extraordinarily detailed technical report, almost instantly, without benefit of research facilities or resources." - Alan Carson