In addition to the Sheldon Brown article and texts others have referred to, check out Peter White Cycles websits. Peter is one of the foremost names in wheelbuilding in the US, and he has helpful articles and a forum he hosts that are excellent resources.
I'm also a big rider and got into wheelbuilding for that reason -- but, and this was a huge revelation -- I got a set of wheels built for me by Peter White that I have now ridden about 2000 miles and have never even needed truing. Get a strong enough rim (your Rhynolite, or Velocity Dyad, or the Mavic touring rim PWhite discusses on his site) and go with a higher spoke count like 36-40 and you should never have problems. PWhite guarantees his wheels for life.
To de-tension wheel while building, take it off the stand -- rest it on edge on the floor on something that will cusion the rim, and put some downward force on it -- not a ton, just enough to compress the rim a bit and allow the spokes to unwind.