If my memory serves me correct they tend to wear grey wasitcoat type, blue trousers and have a camera around their neck.
Also they tend to jump out at you asking if you want your photo taken usually in a popular place.
Magic Kingdom
Infront of the castle anywhere from the start of main street up til the crossroad area.
Sometimes with a character.
MGM
Usually the start of the street
With Characters
there is a place where you can your photo with Mickey next to the backlot tours.
Animal Kingdom
Infront of the tree of life
On the bridge over the water also a tree of life photo.
With characters at camp minie and mickey
With character tigger, pooh, piglet and eyore this is near dinoland
Epcot
The entrance
inside where the characters are
Sorry my memory has gone blank on the names, i just tend to go without thinking.
Also the photopass photographers carry a black hand held device with scans the card.
Hope you understand