The best performer I've ever had the privilege of working with is Don Schuerman.
I've known Don since 1994 and have been performing with him for almost as long and I have never worked with someone who is such a complete comedian. Actor/Director/writer/musician, the man can do it all and do it well; on top of that, he is one of the smartest performers I've ever seen on stage; AND ON TOP OF THAT, he is an amazing and generous human being.
"Play at the top of your knowledge" is a borrowed phrase that has been bouncing around the improv world for a couple of decades at least. I first heard it in 1999 from Joe Bill and he later refocused that same idea with the note to "Play at the top of your integrity". As a director, when I say "play at the top of your knowledge", I'm fully aware that the upper knowledge threshold is something different for each one of us. We all enter the stage with different experiences and knowledge bases. That's what makes improvisation amazing; to make it successful we create a world that is a meeting point of our mutual ideas. No two scenes can ever be the same because who you are at any moment in time is completely different from who you were the last time you did a scene. It's one of improv's uncertainty principles. For me, playing at the top of your knowledge is not about playing snobby uppity intellectuals, it's about playing characters who are trying to get through their world the best way they know how.
I consider myself a fairly intelligent person. I try to keep abreast of as many topics as possible. Some things will stay in my brain for a while...other facts are more transitional and leave a few days or even hours after I try to force them into a mind crevice. Some of us are just able to retain and regurgitate an amazing amount of information...Don is one of those guys. He is a walking encyclopedia/dictionary/Human Search Engine on an amazing amount of subjects. Regardless of the suggestion from the audience, you know that Don is going to have at the very least an idea of what it is.
However, regardless of the number of references he can drop in a scene, there is still a basic skill that he utilizes that anyone of us can learn from. He makes a scene real by painting it with grounded details and interesting facts. He doesn't smother a scene with references...he merely drops enough specificity to make the scene real for the audience and the actors. With Don, you can do a scene almost anywhere in the world at any point in time and he will be able to stitch a detailed reality.
Anyone can define a who, what, where and have it be supported by some edits that paint the scene. The true skill is to be able to lay down references and facts that draw upon our collective knowledge to then paint the scene in the mind's eye. This is what Don does very well. Then, once the scene is set, he digs even further into his knowledge base to build out the relationship of the characters. His attention to detail in a scene is so exquisite that you feel that if you were to commit any more to the scene, you would will the reality of the scene into our dimension.
Many directors advise that you should immerse yourself in as much knowledge as possible. As a young improviser I bought several cultural reference books just so that I could know a little bit about everything. These days, the internet, twitter, facebook and RSS feeds makes it a lot easier to cultivate news and data. I think that the knowledge immersion advice will always be applicable...but I personally believe that you should go further. Don't just develop your referential and factual knowledge but also develop your experiential knowledge. Force yourself to try new things that build upon your existing comfort zone. Force your brain to have to learn and comprehend a new emotional context or frame of reference. Break your routine, try something new, force yourself to engage in a new environment with new people and raise your upper threshold of experiential knowledge.
I have found that my clearest and longest lasting memories are the ones that lie right outside of my routines. New places I visit, unique meals, people I meet create a fresh foundation in my brain and tend to stay there a little bit longer. These are now fresh pieces of information that I can draw upon later. I can do scenes about cooking Burmese food and road-trips in Alabama because now, I've done both of them. If I ever have scenes that will require any of that information, it is there for me to use.
Developing your knowledge and breaking your routine helps you further realize the importance of patterns. You start to see that patterns aren't just something that exist on stage within a warm-up exercise, scene or a 25-minute set. Patterns begin before your set and continue after it. There are behaviors, situations, relationships, people that exist all over the world that are part of the same patterns and with an increased experiential knowledge base, you can make those more universal connections. It's this pattern recognition that resonates deeply with the audience because those are the patterns that they identify with in the real world. It's when we're able to find and explore those universal patterns that speak to larger truths that improv elevates to a special place that is at the same time hilarious, magical and profound. Like Don Schuerman.