Here is an interesting attempt to make the Drake equation more accessible:
I like the fact that they have the various standard assumptions, from optimistic to skeptical. I’ve always erred on the side of the optimistic on this one. It just strikes me as just one more example of human arrogance to conclude that we are special in this galaxy. One thing I’ve always liked about the Drake Equation is that it focusses the discussion. It takes a totally impossible question (“how many intelligent civilizations are there in the galaxy”) and breaks it up into a number of smaller questions, many of which are answerable. Of course, near the end of the calculation it gets a little dicey, but so are all such problems.