Substitute cornstarch for part of the flour. Moist steam causes the average flour-based waffle to soften as it cools. Add cornstarch to the mix, however, and you increase the waffle's ability to hold moisture. As a cornstarch-enhanced waffle cools, moisture does not escape as quickly as if it had been made with just flour, and therefore the waffle stays crisper longer.
Separate the egg and whip the white. Waffles made with whipped egg whites are not only lighter and more airy, but also taller and more tender. Plus, they brown better.
Add sugar to the egg white rather than to the other dry ingredients. Beating in sugar softens and stabilizes the egg white, making it much easier to fold into the batter and improving the batter's longevity.
Add a generous amount of vegetable oil to the batter. A thin batter generally produces a crisper waffle. So a liquid fat, such as vegetable oil, makes a crisper waffle than one with solid butter or shortening. Don't skimp on the oil: Waffles made with relatively high amounts of oil are crisper.
Use a mixture of buttermilk and milk rather than just one or the other. Buttermilk waffles are more flavorful, but the batter is thick and the waffles are less crisp. Waffles made with milk, on the other hand, are more crisp, but less flavorful. A combination offers the best of both: milk for crisp texture, buttermilk for full flavor.
Add a touch of vanilla extract. Vanilla extract improves the flavor so dramatically that I often eat my waffles without butter or syrup.
Set the cooked waffles on the rack of a preheated 200 degree F oven for at least 5 minutes before serving. The warm oven accomplishes two things: You can make all the waffles before serving, so everyone can eat at the same time. And the low heat beautifully reinforces the waffles' crispness. Do not stack the waffles: They'll turn moist and limp within seconds. If you forget and stack them anyway, don't worry. Just separate them and place them in a single layer again. They'll crisp right back up.