It depends if you want to be entertaining or informative/thoughtful. For informative/thoughtful, you basically need to have coherent thoughts on a given subjec

It depends if you want to be entertaining or informative/thoughtful. For informative/thoughtful, you basically need to have coherent thoughts on a given subject before you speak. You can't just magically figure things out as you open your mouth, there isn't nearly enough time. For entertaining effect, I guess it's more art than science. Try watching some good sitcoms and standup comedians perhaps?