Ah, well - you know the rhyme 'one for sorrow, two for joy...' etc? It's an old wives' tale that if you see a single magpie, and salute it (with your left hand, I believe) and wish it good morning (has to be in the morning - and you have to call it 'mister'), then you don't get the sorrow.

Explained more succintly here. Idk, we're weird in the UK? Plus, there are a multitude of variations on this salute, including turning on the spot, and spitting on the ground, or something. But I don't go in for that. Mainly because it would be awkward when I see them while driving. >_>

...my pups are staring at me as though I'm a twat. All of them. Well, it's probably deserved. :\