Work the interviewee's name into your sentence if you wish, then add a parenthetical reference to the nature of the communication and the date on which the interview took place. For example, if you interviewed John M. Smith about the color of the sky on June 1, 2009, you could refer to the interview as follows:
J. M. Smith suggested that the sky sometimes appears gray, white or even black based on conditions such as clouds or time of day (personal communication, June 1, 2009).
Include a parenthetical reference with all the information about the interview if you do not wish to work the interviewee's name into your text. To use the same example, you might say something such as:
The sky does not always appear blue; its color can range from white to black in certain circumstances (J. M. Smith, personal communication, June 1, 2009).
Write your reference list without including the interviews. In general, every source you cite should have a corresponding entry in your reference list. Interviews are one of the few exceptions to this rule of thumb.