Weight Distribution - Get as close to 50/50 as you can
A common misconception is that FWD cars need to have as much of their weight over their front wheels as possible to aid traction. This isn't really the case in a track car. More static weight on the front wheels equates to increased load on the front end during cornering and braking, which means that you will overwork the front tyres and brakes over the course of each lap. What's worse, you will be taking load away from the already under-utilized rear tyres, wasting precious grip in the process.
Building a front-heavy car isn't great for driver feel either. Cars rotate around their center of gravity, and the closer the driver sits to that CG, the more natural the car feels. If the CG of the car is too far in front of the driver, the car will feel like it's turning less than it actually is. Most production FWD cars come with over 62% of their weight over the front axle, which puts the car's CG somewhere inside the dashboard. Don't make it worse by moving it any further forward.
Remember RealTime Racing's B15 SE-R? This car had around 55% of its weight over the front axle, giving it a very natural cornering attitude. RTR had to go to extremes to achieve this, including an aggressive lightening of the front end and moving the driver's seat into the area originally intended for rear passenger legroom.
For the practical racer, what this means is to focus your efforts on the front end of the car. Battery relocation, removal of heavy brackets, strategic removal of soundproofing, and even gutting the underside of the dash are all options to take weight out of the front. Conversely, it makes sense to leave some weight in the back of the car, especially if it's low to the ground. For example, don't scrape the soundproofing off the underbody aft of the rear axle. It's not big enough of a difference to help your acceleration or braking, and it will help your car during cornering.
Use Cheap Brake Pads on the Rear End
This one is more a product of necessity than anything else. As you get faster and faster, you will notice that you are constantly locking up the rear brakes under hard braking. Changes such as decreasing the weight over the rear axle and running sticky tyres will cause the brake bias to naturally migrate rearwards. To counter that effect, you will inevitably have to do things to push the brake balance forwards again. Installing install brake bias adjusters, using bigger front rotors, and running more aggressive pads are all ways to achieve this goal. But there's an easier way to tackle this problem - Take those trick racing pads out of the rear calipers and install the cheapest, crappiest auto parts store pads you can find.
As bizarre as it sounds, almost all fast FWD cars use OEM-style pads in the rear calipers. Since FWD race cars tend to have low minimum chassis weights, there's often no need to upgrade to bigger calipers or rotors in the front. Instead, drivers will install more aggressive pads up front, cool them with brake ducts, and use the least grippy brake pads they can find in the back.
On the left are the Raybestos ST-43, some of the most aggressive and versatile club racing pads available today. A set of front pads for a 93 Honda Prelude Si costs $216 from BestBrakes.com, and lasts almost a year. On the right are a set of Raybestos Service Grade Ceramic Brake pads, my rear brake pad of choice. A set of rear pads for the same car costs $7.99 from Rockauto and lasts almost forever.
That's not to say that the rear brakes are worthless in a FWD car. They do work, mostly at the beginning of the braking zone when you have just started pressing the brake pedal. It takes a split second for the load to transfer to the front axle and until that happens you have enough rear grip to use the rear brakes to their fullest. But when that time period is so small and there's so much weight over the front wheels, it's more practical to give some of that up to prevent you from locking the rear wheels. Not only is it easier for the driver to manage, it's also easier on the driver's wallet.