NOTE: This guide was written for F1 2011 but it's completely relevant for all F1 2012 and until KERS and DRS are removed from the game.
Codemasters F1 2011 introduces two new features KERS and DRS. KERS offers a 80bhp power boost for approximately 8 seconds, while DRS is a drag reduction system, providing lower downforce and therefore higher speeds to the cars.
The use of KERS and DRS in qualifying for an F1 2012 brings a small strategy element to the effort.
KERS can be applied at any time there is energy in the batteries. If in cockpit view this available energy is noted by pressing your KERS button. If nothing changes on your wheel (no K beside the KERS value), you have nothing left. Otherwise you can use KERS. My qualifying strategy is to save all my KERS for the end of the qualifying out lap. Toward the end of this lap, start using KERS at a time where you'll run out of KERS as you cross the start-finish line, where it will be recharged again. I prefer to save my KERS for when I'm in the mid to high gears, 4th or above and on a long straight. Deploying KERS at a low speed may help, if you're geared for it. Otherwise you could just be generating wheelspin and wasting KERS.
Whether or not you use all the KERS before the start/finish straight of your hot lap is track dependant, but I like to save a bit for the end, particularly if I'm going to go for another hot lap. If you're happy with your sector 1 and 2 times it's a good idea to burn through your KERS before the last corner of the lap, preferrably when existing low speed corners once you've got traction and are not going to spin the rear wheels.
As DRS usage is unlimited on qualifying laps, I use DRS whenever my front wheels are point straight and I'm past the apex of a corner. I manually turn off DRS prior to entering corners where I'm not using the brake.
The same amount of KERS is available during the race as in qualifying. DRS is limited to only one or two places on the track and then only when you are within 1 second of the car in front at the activiation zone. And then, only from lap 3 onwards and not in wet conditions.
KERS should be deployed at the start of the race once your wheels stop spinning. How much you use depends on where your car is positioned (who is in front of you). If you've got drivers in front that will be slower off the line but are blockers, you may not want to use your KERS off the line, as you'll waste your advantage. Wait until you are right up behind them.
Once the start procedure has been completed KERS can be deployed as per a qualifying lap, when you are in clear air.
KERS introduces some options for defensive and aggressive driving, using it's power boost to both help defend against cars looking to put a pass on you, and you wanting to make a move on a car in front. Most tracks only have a few passing opportunities and your KERS should be saved so it can be deployed at this places, to maximise your drive out of the corner. To that end, if using KERS to pass it's adviseable to get your car pointing out of the corner as earlier as possible, especially in comparisson to the person you are attempting to pass. This will ensure your have maximum grip and can make the most of the extra power at your disposal. Again, be careful to not spin the wheels up when deploying KERS or you'll be wasting it.
Naturally you'll want to use DRS whever you can during a race.