1)Using egg whites and cold water in the batter gives a light and crispy texture.
2)Don't over mix the batter after adding the flour. Else the tempura will be dense.
3)You can double fry the tempura for more crispy texture.
4)You can use beer or sparkling water for more lighter texture.
5)This is best served piping hot with mayonnaise.
6)You can use any vegetables as you like.