Handling
How your car drives or 'handles' is the most important thing around a track in any kind of circuit racing.
All the power in the world is wasted if you can't put that power to the ground because of worn shocks, springs, or bushes.
Shocks
Good condition shock absorbers will make your car handle better by improving the amount of contact your tyre has on the road. They will also absorb bumps and will help with changes in direction better than worn shocks will.
Springs
Springs also play a vital role in the handling of your car. Stiffer springs mean less body roll which means changes in direction are more precise and more direct. Stiffer springs can also make the ride of your car more uncomfortable too, but there is a balance that can be achieved.
Coil overs
Coil over suspension is more effective and beneficial than a standard set up in that there is more adjustment that can be made. Ride heights can be raised or lowered, and dampening rates can also be adjusted to suit different track or road surfaces. Coil over suspension is typically more compact in design which will leave more room for wider wheels and tyres, and is also lighter than standard suspension components.
There are also a few upgrades that can be installed for a little extra handling performance such as Strut Tower Braces, and aftermarket Sway Bars.
Strut tower braces are a good and relatively inexpensive way of adding rigidity to your car. They simply bolt to where your strut towers are mounted under the bonnet and in the boot area of your car.
There are also various chassis braces that can be added to increase the rigidity of your car.
Sway bars are fitted to most modern performance oriented cars as standard, but as these can be hollow and not that large in diameter, they are prone to flexing. A big improvement can be made with upgraded aftermarket sway bars. These are usually solid and thicker in diameter for added rigidity.
Bushes are often overlooked as a viable handling upgrade, but can make a good amount of performance difference. Stiffer bushes mean less movement of the components that they're fitted to, and therefore will mean better handling overall.
Suspension components that are in good condition will make all the difference with any performance driving, so whether you're running coilovers and a full race setup, or standard suspension in a normal road car, make sure that everything is installed correctly, is safe and legal, and in good condition for maximum driving pleasure and handling.
If ever in any doubt, ask a professional!