There are several common causes of poor quality conference calls:

• People simply not showing up.
• Lack of familiarity with behaviour and protocol.
• Lack of familiarity with equipment and technology.
• Background noise and disturbances.
• Poor coordination by call-initiator.
• Lack of moderator

Each of these causes requires a different kind of corrective action. However, there is usually one primary root cause; for example, people may not be showing up because the technology does not work, or the technology may not work because people are not familiar with it.
Technology problems tend to fall into two kinds: lack of bandwidth and poor equipment. Again, it is worth checking which of these apply in the case of technology problems.