In long, detail-ridden presentations, it's easy for the audience to lose track of the big picture and get hung up on the details. To make sure your audience doesn't get mired in minutiae, introduce the big picture, then go over any pertinent details, then restate the main point to demonstrate how all those details were relevant. Basically, contextualizing big blocks of information, before and after you get into the details, helps your audience to follow you. Watch out for too many words. Particularly when we feel nervous, or like we have a lot at stake, we tend to over-explain things.
More words can often obscure meaning, rather than clarify it.
Instead of talking yourself and your audience into a state of complete confusion, plan in advance how to explain things succinctly and cogently. Besides, in the work world, time is of the essence, so keeping it short and sweet can't hurt. Believe in what you're saying and let your conviction shine through. You don't need to be a zealot, breaking into a flop sweat as you compare your product or your company to the Holy Grail, but DO be genuinely enthusiastic. Getting excited about what you're talking about is infectious.