If you're presenting a PowerPoint presentation and its slow to change

Then make a mental note to advance the next slide a little sooner. You gain nothing by stalling with, "Gosh this sure is taking a long time to come up." When something doesn't work as expected it is best to simply go on with the presentation and usually no one will be the wiser.

You intend to application share during your web conference

Open the application(s) and document(s) you are planning to share prior to the start of your web conference. In addition, use the full screen option for maximum impact.

If you intend to share your desktop (rather than a single application)

Then be careful not expose personal or confidential information, and be sure to close email and instant messaging to avoid pop-ups.

If you want to draw attention to certain points during your web conference

Then use the annotation tools to highlight important information.

If you are recording your web conference

Then be sure to let your participants know at the end of the conference how they can view the archive and when it will be available.