You may have killed! You may have had them rolling in the aisles! You may have gotten a 3 minute standing ovation! . . . but your tape of this event might stink.
I have seen so many tapes ruined (including my own) because the presenter didn't make sure there was a microphone recording audience reactions. This isn't really a humor technique but it is really important for humorous presenters for two reasons. 1. They can better critique themselves after the event because they can clearly hear what material worked and what didn't work. 2. They can get good demonstration materials or make salable products out of their recordings.
Nothing sounds worse than your funny line delivered and then muffled or non existent audience reaction to it. This is because of the fine noise canceling microphones that many people wear on their lapels. IT'S DESIGNED TO CUT OUT BACKGROUND NOISE!
I guess a really good sound engineer/editor could doctor the tape up with canned laughter, but what a hassle to do a perfect job at this! And what if someone finds out which they will if the addition of laughter isn't flawless. It's much easier to do it right the first time and put a microphone(s) in the audience.
If you are taping yourself, you'll need a portable mixing board (any time you have more than one microphone going into the same device, you'll need a mixing board). You'll also want an omnidirectional microphone that pics up all the laughter and comments people are yelling at you . . . .(well maybe not if they're heckling you :) ) Visit a music store that caters to bands for help picking out your equipment.
If you are being paid to be there, you need to nicely inquire about the A/V and depending on how much clout you have see if you can jockey for the extra microphone(s) in the audience. Even offer to pay for it yourself if it means you'll get a better tape.
This little bit of extra effort will mean a big difference in the quality and usability of your recordings . . . and hey . . .if you bother with all this you better be funny.
This and other recording tips can help you make killer Youtube videos that convert to more speaking gigs. Learn the marketing tricks of the highest paid public speakers.