Undoubtedly the best investment in chain care is an oiler, ScottOiler is probrbly the best known, and certainly something I've used for a very long time.
On the Tenere, with a scottoiler fitted from pretty much new, I'm on 14,000 miles and still on the original chain and sprocket set. The wheel has been adjusted back just one notch.
Lots of people mention that you get oil everywhere, and I certainly have small 'drips' from the front pinnion area when the bike stops, I think of it more akin to a dog marking it's territory
However, a small investment of time to get the flow right and you will have no problems, but you have to keep an eye on the flow rate and adjust it as the ambient temperature changes. After a whil you get used to where the gauge should be for what timeof year / temp it is.
Anyone who's seen my bike will confirm that the chain is is 1st class condition and the wheels etc are most definatly clear of oil.
If you preffer to clean and lube the chain, then it will be needing lubed every 100 - 200 miles, on the XJR (no scottoiler) I lube it after every ride (I use wax so the best time is when the chain is still warm).
As for cleaning, on the TTR I use straight forward Paraffin, a tub and an old paintbrush. Kinda like 'painting' the chain, I don't go too far into the chain and just remove the crud from the surface - then clean it off with Mukoff and cold water. I run the chain (on the lift/stand) for about 5 minutes to clear the water away then over lube it with a normal oil based chain lube (Hien Gericke is the current flavour), ready for the next ride.
Whatever you do, remember to lube the chain after the ride, the oil/wax flows into the chain better and it'll stop any corrosion from starting if there is some residual salt (yes, even now it's still there).
There are spray cleaners available for yuor chain, but at �5 or more per tin, and it only lasts two or three cleans, Paraffin is a much cheaper option (at about �5 a gallon), even if you buy the horticultural stuff from Homebase.
WD40 will dispel water, and alos the grease from inside the chain - try to avoid using it (also does the same to the grease in the bearings!)
So, it really depends on how mucky the chain is, how quickly it looses it's lube and what sort of riding you are doing, at 5K miles at year a ScottOiler is probably a reasonable investment (you get 500 - 1000 miles per fill depending on the conditions)
Hope this is of some help to you, but remember it's only my opinion, others opinion may differ.
Darren