Meaning: in a straight line. By the shortest route.

Example:
1. The nearest hotel is about 24 kilometers away as the crow flies.
2. There is a beautiful hill station about 20 miles away as the crow flies, right from where we are standing now.

Meaning: readily won and readily lost. When someone is not overly concerned about losing something.

Example:
1. I won a lot of money at the casino last night but lost it on my way out. Oh well, easy come, easy go.
2. She isn't used to working for her own money, her husband gives her everything that she wants. She has even crashed her new car. I guess it's a case of easy come, easy go.

Meaning: in clandestine, privately, secretly.

Example:
1. The planning board of the finance division constantly meets behind closed doors, in case its negotiations become known in advance.
2. A lot of meetings are held behind closed doors in order to prevent the public from knowing what is discussed.

Meaning: say little or nothing about one's opinions or intentions.

Example:
Our boss is notorious for keeping his own counsel; you never know what he has in his mind.

Meaning: to do something in hiding or secret because it is morally or socially not acceptable. In league, but usually referred as a negative thing.

Example:
1. It is usually the close circle of celebrities who are in the cahoots with the paparazzi. This is how celebrity outings are caught on tape so often.
2. The lawyer was in the cahoots with the criminal in this case. It is unfortunate that they won the case.