I find it really depends on the type of presentation you are giving. I find interactivity in my presentations allow me to get a feel for and tailor the content to the audience. It also removes a lot of the dryness. Things like "what are you thoughts on [topic]" or "[how do you / what would you do to] solve that problem currently". The key is directed questions to prevent open discussions. If of course there is a possiblity for the presentation to go off on a tangent and you should be confident enough to bring it back on subject. If you are against time constraints or not confident of questions through out; I have found something along the lines of "Please leave questions until the end, but if you do have a buring question you are busting to ask or think you might forget, I'll be happy to answer" This stress the fact that you do want questions at the end, but at the sametime has created an initial rapor with your audience and has put them at ease. A good use of animation during a presentation is to put emphasis on key points or to bring the audience's focus back on you. It is suprising how well a light clap of the hands works in a sentence, or when reading short list stressing each item with your fingers. Volume, pace and tone of your voice is extreemly important, of course you should be heard at the back, however they way you speak should add interest. Vary the volume and tone, if you have some thing important to say that you really want your audiance to hear or perhaps you can feel yourself loosing them, try lowering your voice and slowing the pace of speaking just a tiny bit. And the number 1 most important thing that you can bring to your presentations is enthusiasum. Do not expect your audiance to be intrested in what you have to say if you have aboslutly no passion for the subject.