Might seem basic, but most of us are just wait for the other person to stop talking, so that we can say what we want to... That's not where it's at. Hear that person. Listen. It creates a shared experience.
Say YES, and..."
Saying "yes" seems pretty basic, but it's so easy to stop yourself short of what could be just because you decided to say "no". Okay, you got "yes" down? Now add the "and..." That's where the magic happens. Take what the other person is saying and build off of it. One person says “We're in a submarine,” Person two replies, “Yes, and my room has a waterbed,” and on and on until you end up in some weird ass place you never could have imagined at the beginning. If that reality ends up being funny, that’s great, but if it's not that doesn't make it any less improv. It's about creating a world with someone else.
Be in the moment.
You have to be present to really live in that world you just made. I'm working on this.
Every person's contribution is as important as another's
Take chances
...be scared, but keep going.
Follow your own instincts.
Let yourself fail. Go for it.
Odds are shits not going to be funny... especially at first. Roll with it without being judge-y. It's a process.
Keep exploring past the initial thought... that's where the good stuff is.
I found myself thinking of the most obvious and un-funny things, and getting kind of stuck on those concepts. I could have stopped right there, and felt like I was destined to suck at Improv Comedy for the rest of my life. BUT I didn't. I kept thinking about it... It gets funnier after you get rid of all the stupid ideas.
Observe your self talk & see if/how it serves you
This speaks to the past point... you not telling yourself that you're a lost cause because you came up with some tankers. It's cool be patient... You're learning a new skill.
Don't shy away from what you know. Use it!
You're smart. Chances are you know a lot about something. Use it. Talk about baseball if that's your thing, or trains, or whatever... just roll with it. Your perspective is important.