Student or Learner
Did you go out last night?
Yes, but I (had) checked my e-mail before I did that.
-Which one is more common (in this kind of sentence) in everyday English?
Ask yourself, "Do I need the past perfect? Am I being ambiguous by using the simple past?"
You've used the adverb 'before', so the timeline of what happened is not in doubt. Also, there's no logical connection between the two events that might make the past perfect defensible.