There’s one sure way to make your presentation weak. I had the ill fortune 
  of experiencing such weakening a couple years ago. Perhaps you can learn from 
  my mistakes…
  The year was 1997. I was still a novice presenter, and I was to make a 
  90-minute presentation to the NLRB about using the Internet. There would be 
  about 100 people attending. I was nervous.
  I prepared for many hours, and when the day arrived, I was more-than-ready… 
  or so I thought. Aside from the normal anxieties of speaking before a large 
  group, my primary concern was the possibility of technical difficulties. I was 
  away at a resort hotel -- far from the wealth of tech support and back-up 
  plans available to me when making presentations "at home."
  My anxieties, for the most part, were unfounded. My hardware and software 
  worked as advertised, the audience was lively and interested, I was able to 
  answer most of the questions asked of me, and though I ran well over my 
  allotted time, the audience seemed to appreciate my long-windedness.
  Afterward, many members of the audience approached me with questions and 
  comments. The comments were mostly praise, which made me feel just great. Ahh, 
  I thought, this was a good presentation -- and better yet, it was now behind 
  me. 
  But I was in a delusional state. A sobering comment from an audience member 
  quickly brought me out of it.
  "Mike, I really enjoyed your presentation. I just wanted to let you know, 
  though -- and I’m sure not too many people caught it -- but you have a 
  misspelling on one of your slides…"
  I didn’t hear too much after that -- at least not too clearly. It was one 
  of those moments where time seems to stand still -- where objects in your 
  periphery become fuzzy, the volume of your reality lowers to near zero, and 
  you grope to make sense of an apparently incomprehensible situation. 
  During this "non-time" I had a brief conversation with myself, which 
  consisted entirely of mental stuttering. Eventually, I snapped back to 
  reality, where everything was painfully clear, and the gentleman before me was 
  finishing up his sentence, "…so thanks again, and be sure to run that 
  presentation through your spell-checker."
  At that point, I did what I think any sensible person would do in such a 
  situation. I did a big mental scream: AAAAAAAAAAHHHHHHHHHHH!!!!!!!!!!!!!!!!!!!!!
  Then I put on an embarrassed smile (very easy) and thanked him for pointing 
  out the error to me.
  
  
 How could this have 
  happened, you wonder? Don’t most presentation software packages come with a 
  spell-checker?
  Of course they do. I foolishly (yet purposefully) did not run the 
  presentation through a spell-checker because it was so chock-full of URLs and 
  Internet terms that I thought it would take forever to run a spell-check on 
  it. PowerPoint 97, unlike Word 97, does not allow you to set the spell-checker 
  to ignore URLs. (PPT 2000 will ignore URLs if you make them hyperlinks 
  instead of just plain text.)
  Mad as hell at myself, the first thing I did when I returned to my office 
  was fix the one mistake that was pointed out to me. Of course, I also 
  sat down and carefully read through the presentation slide by slide to make 
  sure there were no other abominations in it… since I had a presentation coming 
  up for the FBI a few weeks later. What I did not do, however, was run the 
  spell-checker. That would just take too much time…
  You can see where this is heading…
  The FBI talk was for a group of similar size and importance. Again, 
  everything went smoothly, and when I finished, there was a lot of applause and 
  some formal expressions of gratitude. I was feeling fine. This, I thought, was
  definitely a good presentation.
  As usual, members of the audience approached me afterward with comments 
  that went like:
  "Wow, great job! I really enjoyed your presentation, especially the part 
  about…"
  "Mike, that was fascinating. You know, I never knew that…"
  "Hey, that was a fantastic presentation, though you may want to fix the 
  misspelling on the slide where…"
  EXCUSE ME! AAAAAAAAAAAAAAAHHHHHHHHHHH!!!!!!!
  As you may have guessed, that was no mental scream. In fact, if you were 
  anywhere east of the Mississippi on December 5th, 1997, you 
  probably heard it pretty clearly. 
  When they released me from the asylum weeks later, you can bet that the 
  first thing I did was spell-check that presentation! Yes, I finally sat down 
  and went through the onerous process of having the spell-checker hang up on 
  every part of every URL, on every too-new Internet term, 
  and, of course, on every misspelled word (of which there was only one 
  -- the one pointed out to me by the FBI attorney -- really!). I did not care 
  how long it would take.
  And how long did this take me?
  
  Eight minutes.
  I’m not kidding. I clocked it. Eight minutes.
  This, of course, sent me back to the asylum. But I’m out now -- no longer a 
  threat to myself or others -- and enough time has elapsed for me to be able to 
  tell you about it calmly. I’d like to think that something good has come of 
  these two minor tragedies (it’s the only way I can maintain my sanity). The 
  primary benefit is that I am now a spell-checking maniac. I can’t even 
  scrawl out a quick grocery list now without running to a dictionary. And while 
  hanging out at the other end of the spectrum might not be all that healthy (at 
  least that’s what my therapist says), I figure it’s got to be better than 
  where I was previously -- loserville.
  And I’m hoping that even more good will come of these mishaps -- that 
  perhaps some of you will learn from my mistake. So, if any of you have a paper 
  or presentation that is loaded with uncommon terms (Internet or otherwise), 
  and you are completely lacking in good sense, please take note: USE A 
  SPELL-CHECKER!
  You won’t regret it, and it probably won’t take as much time as you might 
  have guessed. Even if it takes an hour, it will be an hour very well spent. 
  Trust me.
  You can be certain that, before submitting this piece to LLRX 
  for publication, I spell-checked it more than once. You can’t be too 
  careful. One of my mentors told me that I should also be sure to proofread it, 
  but I was on a tight deadline and had a lot of things going on at work -- I 
  didn’t think that it was really worth my thyme.