On Power Point...
I find that speakers are often nervous, it helps to have them practice and practice if they are not used to using PPT. The transition speeds vary from system to system, so practicing on the system you'll use for the show is good to do.
I set PowerPoint to back up on Right click rather than "pop up" the menu... (Tools -> Options -> Uncheck "Pop up menu on right click") This way the speaker can back up really easily if they need to.
Also, printing the Slide Sort as screen shot makes it easy for the presenter to hop around the show if need be. Great for