[blue00gt]

It all depends on how much performance you want and how much you can spend. A lot of people are happy just going the OEM-style component route with chassis stiffening, stiffer springs in the stock positions, better damping, and stiffer sway bars. This route reduces the factory understeer and body roll and is much better for spirited driving.
If you want ultimate performance, you will have to go further with tubular k-member, coilovers, non-stock geometry, and a panhard bar/torque arm or 5-link rear suspension.
Whatever you decide to do, if you can't buy everything at once, make sure you buy components that are compatible with the things you plan to add in the future.
I like Griggs Racing and Maximum Motorsports suspension parts. I've also had some good luck with Steeda.
As for selecting the appropriate spring and damping rates, just call the guys at one of these companies and tell them what you want to do with the car and how you plan to use it.