As opposed to a ski that is out of tune, a ski with a smooth edge promotes easier forward and lateral movement because there is less friction. The higher the degree of the base edge level, the lower the performance of the ski. Increased side edge bevels increase the sharpness of the edge only for short periods of time. Go big if you love to tune. Many competitive skiers choose 3 degrees almost exclusively, but you might want to experiment with your options.
Tools make the tune - buy the best stuff available, and learn how to use it.
Wax, wax, wax. When your spiffy new graphite bases are white, you've got problems. Consider that World Cup Downhill skis usually aren't fast for three to five years, after being waxed almost daily. If you are lazy or don't fancy yourself as a total tech weenie, find yourself a great tuner, a hand tuner, that is. Machines should only be used to accomplish basic foundation work.