I can TOTALLY relate to your post. When I started out in consulting I hated the thought of presenting, almost to the point of making me ill. I made sure I got sent on a presentation techniques course within my first weeks on the job and that transformed things for me. From then on I really enjoyed presenting and now love taking to the stage and addressing hundreds at a time - or being grilled in board presentations.
The single biggest thing to come from the training was confidence. We were all filmed in action and when we watched these films back we saw that actually we were pretty good - far better than we'd feared we were. So if you have any way of filming yourself and then watching this back I'd definitely do this. The practice runs will do you good - and seeing that you are much better than you thought will do your confidence the world of good.
As has already been said on this thread, confidence is key. A presenter lacking in confidence invites criticism and challenges from the audience; one who comes across confidently will often sail through unchallenged.
Other things that came from the training: i) make a conscious effort to speak at half the pace you think is appropriate. Almost everyone has the tendency to gabble when presenting, so it requires a conscious effort not to do this. ii) pay attention not to fiddle with things! Everyone on this training course span a pen in their hand, played with the projector remote control, span their wedding ring, etc. It was just a nervous reaction to take the mind off the pressure of the presentation. But it's really obvious and distracting for the audience and draws attention to the fact that you are nervous. So also make sure you do not have anything in your hands whilst presenting.
The last thing we were recommended to do was to try and make lots of eye contact during the presentation with whoever you feel most friendly with - be that a colleague or whichever of the client organisation you're on best terms with. This helps relax you as you feel like you're presenting to a room of friendly faces rather than a room of potential critics.
Hope this helps and best of luck!