These Flea pictures will give you a good idea what to look for and will allow you to know what you are dealing with.
This is a sand flea.
This is the size of common adult fleas.
This is what a flea looks like up close.
This is flea dirt left behind by fleas on a dog.
Fleas are very creepy looking when you zoom in on them.
Here is a clump of fur with lots of flea dirt in it.