I want to do something that the first time you click "look at" for an NPC it says something, but the second time you click it, it changes the description or the verb "look at" for the rest of the game to a different description

If it's a text description, {once:This description will appear the first time.}{notfirst:This will appear every other time}

If it's a script, you can do:

firsttime {
  msg ("You look at the guy, but he's too boring and you don't learn anything")
}
otherwise {
  msg ("I'm not going to waste any more of my life looking at that dude.")
}

Same thing, different example.

look at guard

firstime {
  msg ("A tall man in leather armour stands next to the gate to the castle. He notices you and says,")
  msg ("\"<i>Eh, move along there peasant!</i>\"")
}
otherwise {
  msg ("A tall man in leather armour stands next to the gate to the castle. He looks at you sternly.")
}