Images from http://www.cichlid-forum.com/
Most long time cichlidophiles can identify cichlid species quite easily. Just like true gearheads can quickly identify cars without the benefit of seeing the make's logo, experienced cichlidophiles can tell what species they're looking at by just the shape of the body and/or tail.
If you're new to cichlid keeping and need a bit of a primer to help you identify an African species, check out the Cichlid-Forum.com's nicely assembled chart. It's neither comprehensive nor exhaustive but it does provide a nice color pictorial of the more popular African's in the hobby.
The Cichlid Room Companion
Tropical Fish Hobbyist
American Cichlid Assoc.
African Cichlid Hub