Karnij, I'd be surprised if more than one in a hundred riders have a clue on how to lube a chain. Most just use what I call the add, add, add method. They just keep spraying on more and more layers of some filthy, sticky goop that does nothing but attract and hold huge amounts of road grime and grit. WD-40 has only one possible use here and that is as a cleaning agent and should only be used as a substitute for proper cleaning. The point to remember here is that nearly all chains are O-Ring or X-Ring type and as such you can't get any lube into the load carrying pin area anyway. Other than lubricating the rollers, a chain lube only serves to protect the chain from water and corrosion.
Kerosene, WD-40 or other thin oils can flush off much of the dirt and grime but they're oils and will leave an oily film all over everything. You don't prepare to paint a wall by spraying oil all over it, do you? You want the chain to be absolutely clean and 'free' of oils before applying chain lube. I prefer to gunk my chain during a typical washing. Gunk makes the kerosene water-solulable. When the bike and chain are clean you must then get all the water off the chain, as you don't want to seal any water hiding beneath the rollers under the lube. If you donít have an air compressor you can simply take the bike for a short ride to sling off any water. Then apply a good quality chain lube; I prefer chain wax, for several reasons. Last and perhaps most important you must now wipe off all the excess lube. I use a loose nap towel, such as an old face towel. Be very careful here not to get your fingers caught between the chain and sprocket. You'll need to get the rear tire off the ground to do this effectively, but that's another subject.