Nothing special really, it's just about making the front spoiler as low and wide as possible to block air from being able to flow under the chassis and cause the car to lift off the ground at high speeds. Of course you can't make it too low for a street car then it would be scraping on everything. But take a look at modern race cars, if the rules allow it they run them almost touching the ground at ride height for max air deflection. Shape can come into play but the cars we're dealing with are basically flat in the front so it doesn't matter too much for our application.
