If you are the main speaker for a conference call or web conference, you may want to practice before the day of the phone call or event. You can assure yourself that your audience will get the full impact of your message by taking the time to be well prepared. What you really shouldn’t do is try to conduct a conference call in an "off the cuff" fashion.
Prepare your notes ahead of time
Think about the main topic, what you want to say, and the length of the conference call as you compose your notes. Remember that people in other places will be listening, but not seeing you. They will likely be taking notes themselves, so you have to present your theme in a digestible fashion.
Practice going over your notes
Once you have your notes in good shape, it is time to practice saying them aloud. You cannot replicate what will happen during the call, but you can be familiar with what you want to say. You could tape record yourself reading through the notes and play it back to get an idea of how you might sound. Or you could ask a friend if you can could them and go over the notes. This person could ask you a few questions and give you feedback.