When getting or giving directions I always prefer a map to written directions. Maps are great because they don't become useless if you make a wrong turn. With a good map you can always find where on it you are and can always build a new route to your destination.
Unfortunately, one can't always produce a map on the spot -- especially a good map. In those cases you have to fall back on written directions. I've given and received plenty of directions, some good, but mostly bad. I'm thinking a list of guidelines to use when vetting directions could help.