When you're setting up a microphone, take a look at the room first for noise sources. Are you close to a window that's looking out to a road? Are there any running fans in the room, any air vents? Is there a TV or computer making noise in another room?
Once you know where the noise might be coming from, do your best to point the microphone away from those sources as best you can. In a perfect world, the only thing that should be in front of that microphone making noise is you.