Take a look at this text about scientific presentations:
They have nice tips for more technical presentations.
useful webpages and notes about making effective scientific presentations in English
"This web page presents a free collection of teaching slides for you, the instructor, to use when you discuss presentations in your engineering and science courses. These slides have been used with much success in presentation courses for engineers and scientists at Sandia National Laboratories and several universities including the University of Barcelona, the University of Oslo, and Virginia Tech."