Hoover all the crap off them, then use a soft brush with the Autoglym Interior shampoo. And leave the windows/doors open if possible to let it dry naturally.
Roughly from my Autoglym Car Care
Guide
What he says... don't use the car if it rains, the rain will bring the stains back / banish all liquid items from entering the car....
On a serious note, use the AutoGlym Interior Shampoo and when the seats are dry spary some generic fabric snoe protector on them and this should give you some time before the stains return.
My Mum has an Audi A3 and it suffers from the same
problem in the "wet" and thats on a 16k car, must just be the fabrics that the VAG group use that leaves them open to staining so easily... Although i'm sure you'll find some people on here that this
doesn't happen to as it does seem to be one of those quirky "VAG" things... for instance my Dad had has an 04 plate Cordoba and he doesn't have this issue and his seat fabric is the same pattern as mine....
.G.