to look on the bright side = to try to see something good in a bad situation
Whatever happens, I try to look on the bright side of life.
to look down your nose at … = to think that someone is less important than you or that something is not good enough for you
She seems to look down her nose at everyone less educated than she is.
Look before you leap. = Think carefully about what you are about to do before you do it.
Going to buy this second-hand car and participate in races? Look before you leap.
to look for a needle in the haystack = to look for something that is incredibly difficult to find
Looking for this old document here is like looking for a needle in the haystack.
to look as if butter wouldn’t melt in their mouth = to appear to be cold and unfeeling (despite any information to the contrary)
He might look as if butter wouldn’t melt in his mouth, but deep down he is a kind person.