Years ago Allen Iverson, the Phiadelphia 76ers' star player, was confused about why the press was discussing why he missed practice in a press conference. He spent several minutes in the press conference (where he said "practice" 20 times) going through his diatribe about why they should leave him alone about him missing practice. It's a hilarious clip by the way (http://youtu.be/eGDBR2L5kzI - for you viewing pleasure). Sports are all about muscle memory, so the more you practice the better you become. If you look at clips of Steph Curry (23-0 record this year) this year, he attributes all of his current success to relentless practice. He makes those crazy, wack shots because he practices them everyday.
This notion of practice plays out in every aspect of life. It affects how you perform at the job,in a sport, and EVEN at pitch events. People say, "you play like you practice" or they say "piss poor preparation leads to piss poor performance." It all lends to the same conclusion, you do better if you practice.
Now "everyone" knows this, but most don't do it. Pitches should be practiced how they will eventually be performed. Take the time and create a great script. This could be one line for a 30 second pitch or several pages for a 5 minute pitch. As the pitches become more detailed and long, you have to make sure that you put the preparation time into the pitch, so that it comes off natural and effortless. Steve Jobs didn't just practice his famed speeches the day before. I'm sure it took months and worked with tons of team members to create the perfect product. Perfection takes TLC and time. Treat pitches like any other high stakes deadline and you will give it the effort required.