Maintenance as my Derailleur are squeaking due to the everyday use and carelessness shown while changing gears while the cycle is static What extra steps should I take to extend the life of the Derailleur gears on my Btwin Rockrider 340 besides oiling them ?
My guess is that your chain is squeaking as it passes through the derailleur pulleys because it is dry.
Cleaning, lubrication and correct adjustment are the keys to long life with a bicycle.


If the chain is dry and not dirty all you need is some bicycle chain appropriate lubricant (lots of choices)
If the chain is dirty and dry you can clean the chain on the bike (a quick Google of "bicycle chain lubrication" will give you lots of information)
If you lubricate the chain and it is the derailleur squeaking use a bike appropriate lubricant on the pulleys and the pivot points on the derailleur. 


Changing gears while the bike is not moving may cause the cables to stretch and effect shifting quality, but it's unlikely to cause the derailleur to squeak.