1. Undo the bit in the base of the seat post with Alan key.
2. Remove spring.
3. Remove saddle
4. Undo red screw cap holding on rubber seat boot
5. Take out inner seat post pole
6. Remove rubber boot
7. Clean everything
8. Grease everything
I think that's most of it - mines due a service, but its been smooth for a few months now, so haven't got round to it.