Rule of thumb is if there's any kind of time indicator word present, the simple past will suffice.
Upon popular demand, here are some examples:
We met at the usual place outside the park. She waved and said hello,
and I said hi and smiled courteously. She wore a very quaint-looking
hat. I realized I had already seen it earlier when we went to
the opera together.
Clearly they went to the opera before meeting outside the park. Yet the presence of the word "when" nullifies the need to use the Past Perfect.
After I told her she had no business yelling at everyone, her behavior became much more ladylike.
No need for the Past Perfect.
I was a total scatterbrain before I met you.
No need for the Past Perfect.
Here are some examples where the Past Perfect is necessary.
From Lolita by Vladimir Nabokov:
For a moment or two, she peered at me with smiling curiosity. She had done it at our first meeting, I recalled, but I could afford then to scowl back.
Note the past perfect in the beginning of the first sentence; but note also it changing to the simple past when the word "then" is introduced to the equation.
From Amadeus by Peter Shaffer:
At that moment I knew beyond any doubt. He'd had her. The Creature had had my darling girl.
Here one of the characters, Salieri, describes a scene that occurred in the past, in which scene he took part. Something he observed during that scene told him of his mistress' infidelity: he realized at that point that Mozart had slept with her.
From Othello, by William Shakespeare:
I did not think he had been acquainted with her.
Here Iago is talking about some point in the past when, according to him, he had no idea Cassio knew (had met, i.e had been acquainted with, had had no prior relationship with) Desdemona.