I'd say start a blank document, and copy/paste any info and links that interest you. There is so much info here, its very hard to find a certain link a month later. Can you estimate your flow speed, and volume per minute?
Better to copy more posts than you think you'd need and then delete a few later.
"Head" is how much altitude between the highest part of the water flow that can be contained, and the lowest spot where the water can be exhausted and still flow away from the exit.
If there was a waterfall coming off a 100' high cliff, and you contained the top into a dam and pond (which has a controlled overflow back onto its original path) and you ran a water pipe from the pond down 100' to the bottom...the pressure at the bottom of the pipe would be about 43-PSI. (~4.3-PSI per 10-ft)
Somewhere between 30' and 70' of head, there's enough pressure to make using a Pelton or a Turgo worthwhile. Somewhere around 100' and above, its useful to consider a centrifugal turbine.
Here's an interesting small-scale, low-head turbine:
http://www.fieldlines.com/story/2008/6/22/191210/965
