If possible, always use a phone with a handset that is hard-wired into the phone lines. Be sure to TEST the working condition of your equipment before an important conference call!

Cellular or cordless phones are more likely to cause static or other distracting noise that they pick up on the airwaves.

Speakerphones pick up lots of background noise, and sometimes cause "clipping" because of the limitations of the equipment. If you are using a speakerphone, try to find one that is "full digital duplex"--this will allow all parties to speak at the same time with no clipping. And if no one in your room needs to speak, use the "Mute" button on the phone to prevent background noise from disrupting conference calls. When someone needs to speak, simply release the "Mute".