Had been waiting: how long before

Had been + -ing: how long before

For how long something went on before a past moment, use had been + -ing (the past perfect continuous):

• She had been waiting for an hour when the bus came.
• He was out of breath because he had been running.

She had waited an hour sees the wait as one finished block. She had been waiting for an hour puts the long wait in front of you. Verbs for states (know, like, have for owning) stay simple: I had known her for years, not had been knowing.

Where else the past perfect turns up

• The third conditional: If I had known, I would have called. See conditional sentences.
• After the first time and best ... ever: It was the first time she had driven at night. It was the best meal I had ever eaten.
• Telling what someone said: "I saw him" often becomes She said she had seen him. See reported speech.

Common mistakes

Don't use had for every past action. I got up, ate and went to work is a simple list: no had needed.