Here is a link to a free and useful program:
http://beercalculus.hopville.com/recipeYou can build a recipe and calculate the amount of strike and sparge water, and the necessary temperatures.
When mashing, you want to target a specific grain weight : water volume ratio to maximize enzymatic activity, and therefor grain conversion (sugar extraction from grains). A good ration (that I always use) is 1.25 qt : lb grain, however depending on your setup, or the recipe, this can range from 1qt : lb to 3 qt : lb grain.
The volume of water used for the sparge is determined by the ration of strike water you use, and the amount of grain. Since grain will typically (although not always) soak up about 0.125 gallons water per lb grain, you wil then calculate how much water to sparge with based on your target boil volume.
Ex: 10 lb grain
@ 1.25 qt:lb = 12.5 qt strike water
Assuming 0.125 gal/lb absorption = 6.25 qt wort available (1st runnings)
To bring the initial volume to 6 gallons pre boil you will want to add 17.75 quarts of sparge water. (good website to calculate sparge water temp:
http://www.rackers.org/calcs.shtml)
This is likely lots of stuff you guys already know. My advice would be to keep careful notes of volumes and temperatures of all the water you use, this will allow you to calibrate your own setup and give better, and more consisten results. BeerTools is the program I use, and for $28 it is worth every penny. It can mke brewday go lot smoother sometimes.