As per GG really - I've got an old chamois to wipe things down everytime I do I "regular" wash but, when needs must there are a couple of tricks I have.
The first is simply water+washing up liquid. Seriously, the grease-breaking-down-additives in household washing up liquid removes a fair amount of grease and grime. I use an old sponge with said solution to give most surfaces and parts a clean. So long as you don't soak the sponge/cloth then no water should get into places it shouldn't.
Secondly, carbourettor cleaner or a similar product will disolve dirt/grime in an instant. Use it carefully as this stuff can get into places it shouldn't, so spray onto a cloth/old rag rather than directly onto your engine. It kind of goes without saying that make sure your engine is cold and there are no naked flames around whilst using these sort of products...
If you want to be pedantic then dismantle what you can (ie engine cover, airbox, battery and battery box, etc) to get at those areas not normally seen to ensure an all-over spangly look.
