Two major things I learned were
a) you have to get the audience hooked in the first 20-30 secs or it gets much harder. Best example Emo Philips opening with “You know it’s really hard when you have to kill a family member because they are the devil. <Pause for laughter>. Other that it’s been a great day”. Now that’s a hook :-)
b) the concept of “laughs per minute” - ie there is a certain rate at which the laughs become self sustaining. It’s 3-4 laughs per minute. If you can keep that up for 2 mins the audience is in a state of laughter that keeps getting more and more intense. If you do less than 2 laughs a minute the energy drops between each laugh and you have to work really hard to bring it back to level. Key is to maintain a rate that results in a high ambient level of hilarity bordering with at least a couple of people cackling loudly and losing it.
Nevertheless when you do a successful set you feel like Superman when you walk off the stage.