Well, here's my childhood remembrance. First, if you see a ladybug flying by, stick out your hand and for some reason she(we always assumed it was a she) will very likely light on your hand. She looks just like the one gnomad showed us, a few posts back. Hold her very close to your face, and tell her, softly:

Ladybug, Ladybug, fly away home
Your house is afire, and your children alone!

She will sit still and listen, until you say this about three times- then she first flutters her wings, then flies- first outward, then upward, then disappears towards the sun. Dad told us she disappears because the sun gets in your eyes, looking after her.

Mom told us it was very good luck to have a ladybug land on your hand, and that we should never harm her.