The quickest way to recognize all the hiraganas and katakanas is to memorize them. Find the hiraganas and katakanas table to study them, it should be arranged to read from top to bottom, right to left.

I think you just have to study both and memorize them. You could probably do it in less than a week. If you don't need to learn them, but only recognize which is which, then I would say that generally, hiragana uses more rounded strokes and curves. Katakana has more straight lines and angles.