Where you start will obviously depend on what you're driving, and what type of brakes it already has. If you're one of those guys still cruising around with four-wheel drums and a single-circuit master cylinder, you won't believe the difference a properly designed and installed front disc brake system can make. For some cars, front discs were optional and can often be retrofitted either with used parts or with new hardware from aftermarket suppliers like Master Power Brakes or Stainless Steel Brakes. Some vehicles were never offered with discs, but for many of the popular applications, retro-fit disc kits are also available. But you may want to skip over the stock '70s-era stuff and go for something a little more contemporary-like the PBR-based systems offered by Baer Racing for many classics and musclecars. Wilwood offers its own version of updated braking with four-piston aluminum calipers and lightweight rotors as well.
Maybe you drive a fourth-gen Camaro or late-model Mustang GT. Both came with very capable four-wheel discs from the factory, but both could be even better. Again, the aftermarket can help to take braking to the next level. Don't overlook the potential improvements just from higher-quality rotors and high-performance pads.
For any of the vehicles mentioned, it should be noted that very often, modern high-performance brakes will require large-diameter wheel/tire combos to clear the hardware. For example, if you install a 13-inch brake kit on the front of your '69 Camaro, don't expect to bolt the 15-inch Rally wheels back on. Depending on the parts used, even 16-inchers may not fit. This can also affect the kind of rear tire and wheel package for dragstrip use as well, necessitating a 16-inch rear wheel and tire for dragstrip jaunts. So once again, research is vital to the success of the project prior to making any purchases. Keep in mind also that full-race brake pads are really not advisable for street use, as the hardcore stuff typically requires a certain level of heat to function. This means that at low temps, there may be little friction, and therefore, little braking. Trust us, it'll make you pucker if you're not prepared. Be real about the use of your car, and remember that there's no shame in swapping pads in the pits at the road course-in fact, it's pretty typical.