In the second case, you are cueing the reader in by showing the character in action, followed by his thought. Often, writers will use flashbacks to show a character s back-story. This can be a tricky practice. A common beginner s mistake is to open their book by immediately taking the reader into the past. Instead, allow back-story to trickle out over the course of the book.
Characters can reveal their past via dialogue or snippets of internal monologue.
If you feel you MUST use a flashback, keep it as short as possible. Begin and end the scene in past perfect tense, but let the rest of the action and dialogue proceed in simple past tense instead of a long internal monologue. He had sneered at her as he d told her good-bye. You ll never be good enough for me, Mary. I need a woman who can stand on her own, not a clinging vine like you.