Wipe it off good, then lube it and run the chain around a few times, then wipe it again. This should be done after every rainy or muddy ride or your going to start rusting (probably only surface though).
Not that I am a qualified expert, but I just read an article in Bicycling Magazine that agreed with Klein. It said that when you finish a ride you should wipe or clean the chain, lube the chain, wipe off the excess, and then let the lube dry. This method is preferred over lubing the chain just before you go for a ride, as so many people do.
The purpose of the first method is to give the lube time to really work its way into the metal of the chain, and to allow an extra lube that is still on there to evaporate. The other problem is that riding with a freshly lubed chain will cause dirt to collect.
I windtrain on weekdays. And I ride on the road during weekends.
I used to clean my drivetrain on Fridays. But now I do it after the 2 weekend rides and on Fridays (after the windtraining sessions).
The chain is far dirtier after the 2 road rides. I has very little dirt on it after the windtraining session which come out to almost twice the hours. So must of the dirt comes from stuff the bike picks up off of the road. I suppose if I were to clean and lube once per week, I should do it on Sunday to clean off the road grit.
I suppose there are 2 reasons for cleaning the chain after a rain.
I'm no expert, but I also agree with lubing the chain after each ride. My basic routine is to lube the chain whenever it gets "dry". After each ride I'll clean it with a rag and then see how much lube if left. If the chain doesn't feel slippery, or it makes noise, I'll give it a coat of oil. Generally my chain loses it's lube faster in wet or muddy conditions.
I lube before every ride. However, I can really see the point of doing it AFTER instead. I think I will start doing that. I do need to do the before thing one more time. I put a new chain on last night.
"There's ALWAYS time for lubricant!!!!" - from Evolution