I typically set bar one, and then tap the tempo for a while.

FYI, there's a lot of music out there that doesn't really hold a tight tempo throughout the song. The chording from the wizard on such songs is so much more accurate if you tap the down beat of each measure throughout the length of the song... Try to be a hair behind the downbeat... otherwise, you'll get leading chromatics where you shouldn't. This will keep the chords aligned with the track, should you choose to keep it attached.

After getting through a number of these imports, you'll really notice artists that use click tracks when they record. Obviously, less edits are required on those import.