i wanted to know that as the title suggests i want to know of the precautions to be taken while opening the case

Don't pinch your fingers Use a little common sence and don't bang around inside the case to hard... Why are you opening the case. To clean the insides?

Nothing to worry about, maybe static. Just keep a part of you touching the case all the time while you meddle with the insides would be fine. Usually my case stays on the floor, with my foot always touching the case.

Haven't had a mishap yet, but most people will recommend an anti-static wrist strap, which just keeps your wrist in contact with your case all the time.

While you meddle with the insides, just make sure you don't put too much force moving things around, if you're taking stuff out to clean. I'd recommend strongly against removing any heatsinks, unless you've got thermalpaste ready, and know how to use it. Make sure you clean all heatsinks. Cleaning fans would be nice, but I'm not sure what kinda improvement you get with fans, but its nice to have everything looking nice and dust-free

If you have carpet flooring, i would suggest wearing a wrist band. It is very easy to pick up static on carpet. I have tile, and have never had a problem with static, even when not wearing a wrist band.

Also if you're pulling or putting cards out or in then be sure to turn off power supply at the back switch as well, otherwise there will still be power supplied to the motherboard. ... other than that make sure you touch the case with a finger first before touching the insides, as others have said.

A simple thing a lot of people forget about: don't stick your screwdriver anywhere near the power supply unless you're an electrician and know how to deal with them. The capacitor in the PSU holds enough charge to kill you.

I'm just sayin' ...