How close my closest focus for each lens is with bellows fully extedended and also without the final extension. This also tells me magnification factor at that distance and how far across the 'frame' is. This allows me to choose the right lens for a macro shot very quickly.
I also have a scale of mm of focus depth vs f-stop vs diffraction effect as taken from the large format photography article on diffraction. This lets me work out the distance between my two desired end focal points and translate that into an f-stop and also, from diffraction effects, how much I could enlarge the picture.
I've also got a table that tells me the amount of coverage that a grad will give me for each lens I own (e.g. a hard grad on my 80mm lens has 13% of the frame covered by the gradation - however my 240mm lens has 55% of the frame covered by the gradation - not so good for hard horizons.. These are the calculations that convinced me I needed some extra hard grads (which singh ray and lee make on a custom basis) - see http://blog.timparkin.co.uk/2008/04/...-graddage.html for details.