well first all the animals in the house need to be flea dipped and treated with a topical like k9 advantix (dont use if the dog and cat groom eachother as advantix is not safe for cats) or frontline plus...
this will help break the cycle ON the pets.
ontop of this he needs to wash everything that can be washed, the pets bedding, anything "soft" they sleep on needs to be washed HOT!.
carpets and furniture shoudl be steam cleaned.
and if the infestation is bad enough, remove pets and people from the house, cover all fishtanks EXTREEMLY well and set off a flea bomb (you can pick up flea bombs at most feed/agricultural stores)
unfortunatly fleas can be a real problem once they get into the house as you need to be incredibly through about cleaning everything. there also rather resilient so when washing bedding and such it should be run on hot and adding bleach will help.
many have great sucess with borax in the carpets before vacuming, and a product called Diamateous (sp?) Earth.
using a topical like frontline plus will help break the life cycle of the fleas so once you get the home cleared itll stay that way.
topicals should be applied once a month and dont buy the cheaper stiff, it doesnt work as well and been proven to cause some pretty nasty reactions.
we use frontline plus of K9Advantix, with you having a cat id probably go for frontline plus.
good luck, i HATE fleas!