1) pick loads of rhubarb. I tend to slice off the leaves right at the plant, and I place them around the base of the plant to mulch it. They break down pretty quickly.
2) chop into one or two-inches pieces.
3) fill a big soup pot
4) add enough water to cover the rhubarb
5) boil until all the pieces have broken down. This is a surprisingly short time.
6) stir up until you don't see any chunks left
7) ladle into a colander over your biggest bowl
8) I found I had to stir the soupy mixture around a bit to speed up the draining process
9) Put the liquid through a finer sieve if you want all the solids out
10) I added filled a quart and added 2 tbs sugar. When serving, I filled a glass half way and filled the rest with cold water. Tastes great chilled.