As with any art form, getting better at improv takes time, effort, and keen observation skills.
For all intents and purposes, improv is a communal art. You can only become a competent improviser if you find at least one other person willing to play with you. This does not, however, preclude you from doing some of the work on your own. If you want to get better at improv, you’ll need to work for it.
“Improv is a communal art.”
Improv is story and character driven; observe the world around you, become a people watcher and discover the characters which are all around you. Follow the stories that unfold throughout the days, and never assume that the seemingly mundane ones are unimportant; they are what life is about, they are the stories that will resonate with audiences.
The key to quality improv is this: don’t be funny, be interesting. The actor who tries to be funny will fail; the actor who tells an interesting story will allow the audience to discover the humor within it by themselves, and when they find it instead of having it thrust upon them, they will treasure it.
“Don’t be funny, be interesting.”
Finally – read, read, and read some more. When you’re done with that, read even more. Books are not all you need to become a good improviser, but they provide an excellent theoretical basis upon which you can build actual experience through group work. Don’t limit your reading to books on improv; read about storytelling, acting techniques, and short stories. Improv is theatre, and should be approached as such. Almost any theatre technique can be applied to improv work if you keep your mind open to the possibilities.
The Big Book of Improv Games – A compendium of performance-base short-form improv games