Lubricating the Chain

I need help with a technical question. How often must one lube the chain? Do you have any tips for doing it the right way? Also, is there any problem with using those chain lube sprays? My mechanic suggested that using the spray would be detrimental in the long run, but I suspect he just wanted to make sure he didn’t lose his business, because then I would no longer have to go to him to lubricate the chain of my motorcycle. Please throw light on this issue.

Harshal P, by e-mail