I've done improv before, and I've found that the best improv comedy troupes were those who were not only funny with comebacks, but read up on the news and kept up with social trends. These helped them perform acts that were affecting people's lives and let them laugh them off. They also watched a lot of timeless slapstick classic comedians like Charlie Chaplin. Some danced to improve their timing in movement; others were in debate clubs that helped them come up with on-the-fly proses. They were big readers, and I think that helped them mince the right words together.