If the primary narration is in simple past, then action initiated before the time frame of the primary narration is described in past perfect. If the primary narration is in simple present, then action initiated before the time frame of the primary narration is described in present perfect. If the primary narration is in simple future, then action initiated before the time frame of the primary narration is described in future perfect. The present perfect is also used to narrate action that began in real life in the past but is not completed, that is, may continue or may be repeated in the present or future. This usage is distinct from the simple past, which is used for action that was completed in the past without possible continuation or repetition in the present or future.
Tense shifts are inappropriate and are indicated in bold .
The gravel crunched and spattered beneath the wheels of the bus as it swung into the station. Outside the window shadowy figures peered at the bus through the darkness. I could not prevent my imagination from churning out a picture of them, the town, and the place I will soon call home. Hesitating a moment, I rise from my seat, these images flashing through my mind. The writer becomes drawn into the narrative and begins to relive the event as an ongoing experience.