Tony Jeary has fantastic tips on presenting. He has trademarked the term, Presentation Mastery - and I recommend his book, "Life Is A Series Of Presentations" - read it and buy it for anyone you know in business. For sales professionals, it is a must.
Check out Tony's PDF on Presentation Mastery from Presentations Magazine. Anyone in selling needs mastery of presenting skills.
Another way I benefitted nearly twenty years ago working on presentation skills, and in the past couple of years as refresher is by attending local Toastmasters meetings. What a fantastic organization - they meet everywhere, at all different times, and each group has its own personality.
Currently I go to clients' sites and videotape their sales reps. We do a group session on tips and strategy, then each rep gets their own time to do a five to seven minute presentation of some type - with on the spot feedback.
Whatever you do - practice. Remember, practice doesn't make perfect --- perfect practice does.