Everything you always wanted to know about champagne but were afraid to ask.

As it is impossible to give a detailed description of the whole process, I suggest that, if you are really interested in the subject, you might buy one of the books written on champagne.
To summarize :
Grapes are harvested at the end of September, beginning of October and the juice is left to ferment until the end of November. The wines are then blended. This is the part of the process which requires the most expertise. In January of the following year, the blended wine is bottled and yeast and sugar are added.
The second fermentation takes place and it is this that produces the bubbles. The bottles are left to mature in the cellars for two and a half years at a temperature of 10° C. The bottles then have the sediment removed and are recorked.