The whole secret of tempura is in the batter, which uses rice flour or a combination of rice and wheat flours.

Here's one authentic recipe (there are many):

1 1/4 cups soft flour
4 tbls rice flour
4 tbls cornstarch
1 1/3 cups water
1 egg, separated

Beat the egg yolk with half the bater. Add the wheat flour, rice flour and cornstarch and mix quickly from the outside of the bowl towards the center. Add the remaining water and stir. Stiffly beat the egg white and fold it in.

Secret two: As with any fried foods, temperature is key. You want to work at about 360-65 for tempura. Under no circumstances should the oil temp be less than 350.

Have everything ready before you start cooking. The veggies should already be skewered. Oil at temperture. Batter freshly mixed.

Dip a veggie piece in the batter, swirling to cover completely. Drop into the oil, a few at a time, so that the oil doesn't cool down too much. Turn, as necessary, to brown all sides.

Serve immediately.

Enjoy!