Don’t fiddle with the mic – if it is a hand held mic, hold it comfortably and firmly then don’t move it because it will pick up sounds of your hands moving, changing over etc.
If you are using a wired mic, try to make sure that the cable is not coiled around on itself or crossing other cables as this can cause interference
If it is a hand held mic, keep hold of it at all times. If you are interviewing using a hand held mic, never give the mic to the interviewee, you hold it for them.
The right distance to hold the mic is about one hand’s width away from your mouth.