Putting audio on the computer via Audacity

When putting audio from reel to reel or cassette to the computer via Audacity or other software it is important not to distort the signal by over driving the audio card from the computer.
If the audio clips, square waves will distort the sound and cause errors in the transition of analogue to digital.
It is best to keep the VU meters just below the maximum level so that the peak level indicator is not stuck at the end