How to annoy your audience
Things to not do during a presentation:
If you are using a web conferencing/presentation tool that supports the upload and display of PowerPoint decks, take advantage of it. Your end users will get a signifigantly better experience than you just sharing your desktop and running PowerPoint on it. Most of these tools understand and can optimize the way a PowerPoint deck is transmitted to the end user, accomodating such things as different screen resolutions, bandwidth, etc.
Bad Excuse #1: "But when I upload my PowerPoint deck to Tool X, my animations are lost/no longer work!"
Response: Then get rid of or rework your animations, they were probably distracting and only marginally improved your slide deck. The words WOW flying in from the left improves no ones day.
If your presentation tool supports Q&A, where users can send signals to the presenter, submit text questions, etc. while the presenter is presenting, have someone else handy to manage incoming questions. This person can filter out duplicates, and restate the question to you, for you as the presented to answer - giving everyone viewing the presentation the benefit of both the questioner's question, and your answer.
An answer without a question is generally less useful.
Bad Excuse #1: "But I don't have anyone to do that for me!"
Response: Then you are ill-prepared to deliver this presentation. You owe your audience a professional and managed presentation. They are spending time listening to you yack, and you owe it to them to come prepared and ready to maximize time usage and deliver information as efficiently as possible. Also, don't be so picky - this person doesn't need to be a subject matter expert.
Never share a blank screen. If your using your favorite presentation tool, make certain that something - anything - is shared at all times. Otherwise, it can be hard for your audience to figure out if something is broken, do I need to disconnect and reconnect, should I ask a support question, what's the deal? Have a "splash screen" ready for situations where your demo explodes, the slide deck got eaten by your dog, whatever - something you can toss up on everyones screen that says, "Hi, this is the title of the presentation you are trying to view, this is the name of your presented, and no you're not broken. We're working on it. Hang on."