Developer, Former MVP, now at Microsoft - Best of 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013
PowerPoint is a great tool for conference (large audience) presentations, which is the context for the advice below.
The #1 thing to keep in mind when you create slides (at least for conference sessions), is that they are there to help you remember what you were going to say (the flow and key messages) and for the audience to get a visual reminder of the key points. Slides are not there for the audience to read what you are going to say anyway. If they were, what is the point of you being there? Slides are not holders for complete sentences (unless you are quoting) – use Microsoft Word for that purpose either as a physical handout or as a URL link that you share with the audience. When you dry run your presentation, if you find yourself reading the bullets on your slide, you have missed the point. You have a message to deliver that can be done regardless of your slides – remember that. The focus of your audience should be on you, not the screen.
Based on that premise, I have created a checklist that I go over before I start a new deck and also once I think my slides are ready.
As always, rules and guidelines are there to be bent and even broken some times. Start with the above and on a slide-by-slide basis decide which rules you want to bend. That is smarter than throwing all the rules out from the start, right?