I attended a public lecture last night, along with a bunch of other scientists. It never ceases to amaze me just how bad some scientists communicate. A few simple tips would most certainly prevent the audience from falling asleep. First, don't use crazy big words (and if you must use them, explain what they mean!). Second, make sure you keep to the allocated time limit (a ten minute talk shouldn't go for 20 minutes...it's bad form). Third, don't say things for the sake of trying to sound like you have something intelligent to contribute to the debate (because it makes you look stupid).