It is best to listen to the guided hypnosis audios in a quiet place where you will not be disturbed. Most audios are an average of 20 minutes in duration. It is advisable to use stereo headphones, but not required.
Hypnosis is not sleep and it is more effective to listen at a convenient time when you will not be likely to fall asleep. While deeper levels of hypnosis are sometimes mistaken as sleep, the difference is directly related to your suggestibility. The subconscious mind is aware during sleep (for instance, you hear someone say your name while asleep); however, you are not in the most ideal receptive state. Therefore, if you prefer to listen before going to bed at night, I advise listening at least once or from time to time during a time when you are not likely to fall asleep.
Please note: Everyone's suggestibility and depth of trance varies. If you are highly irritable or anxious, on certain medications, or in a place where you are highly distracted the audios are less likely to be effective. It is always recommended to listen to the audios multiple times for best results. You are in effect reconditioning your pre-programmed beliefs, habits and behaviors which require repetition in most cases.