Poor recordings can be prevented by testing your equipment before the start of the interview.  Record a quick 30 second warm up question, press rewind and listen making sure you have captured the best audio possible. 

Also, check for optimal placement of the microphone.  The ideal distance would be a hand’s distance away from the speaker.  If in a group, large room setting, placement of several or individual mics around the table will improve the transcript quality immensely. 

Look for any background sounds that may arise during the interview.  Air conditioners and fans have a humming noise that can make it very difficult to transcribe.

Other than digital recordings, standard tapes are the best media for recording, micro cassettes producing the poorest audio quality.