Definitions for "good rule of thumb"
a four-drawer file cabinet per person per year
a good ten gallons per inch of angel at presumed adult size
a ratio of about one tablespoon of ground coffee to every six ounces of water
a film is a success if it makes a substantial portion of its cost the first week of release
a four-stroke needs twice as much displacement to make the same power as a two-stroke
a overnight visit twice a week
a lean protein the size of your palm
a propeller diameter at least half the size of your wingspan
a disfavored city has assumed a disfavored branch
a mile can be crossed in the span of a minute using this ability if there is enough material
a rate of one slide every minute or so of the presentation
a layered approach, just as with firewalls, anti-virus, and anti-spam
a minimum of five years' annual data
a minimum of four and a maximum of eight times a year
a cup of liquid every hour
a travel time of about one hour from your target high school in after school traffic