Modern laptops have Expresscard, or nothing. You can't add a Firewire miniPCI or mini PCI-E card, because they're internal.
Basically, unless you're dealing with laptops over, say, 6-7 years old, assume it either has Expresscard or nothing. There are two form factors, Expresscard/34 and /54 - they denote the width of the slot. /54 slots are compatible with both kinds, /34 slots are obviously too narrow to take a /54 card although the connector is the same.