I've asked around, and I got a couple more tips. The best one, I think is this: knit a swatch. Measure the gauge. Wash and dry it. Measure again. Knit garment to post-washed gauge.
Another tip which sounds bizarre, but they swear it works: when the ribbed edges of the cotton garment have stretched, wack the edges against a counter to bring it back into shape. They say it saves on having to over-wash the garment.
KnittingHelp Queen Bee
"Don't ask yourself what the world needs. Ask yourself what makes you come alive and then go do that. Because what the world needs is people who have come alive." Howard Thurman