i have a question...

'people in glass houses shouldn't throw stones'

my understanding of this is, you're in your house, right, and it's made of glass. you're throwing your stones, ie, calling people names or whatever, and your stone hits someone. they turn around, pick up the stone, see that it was you who threw it because your walls are made of glass and they can see straight through them, and they throw the stone back and it smashes your house.
so, don't be mean to people, because they'll be mean back and it could be worse for you.

if anyone else out there disagrees or can explain it any better, please feel free.

more sayings i don't get...

a bird in the hand is worth two in the bush
that's cheap at half the price!
don't look a gift horse in the mouth