I'm walking into this kind of late - had a very busy few months and haven't been here in a while.
I have been tightlacing on an almost-daily basis for 5 years. My inspiration for it was mainly about reshaping my body, but I absolutely love it. A perfect analogy I heard once is that wearing a corset is like "wearing a hug". As with any other activity, it should NOT cause an undue amount of pain. If so, then it's too tight! Gradual tightening is the key. I was able to immediately reduce my waist by about 6 inches (but I'm a larger person). Thinner people may only be able to start off with a 2 inch reduction.
Some really good reference sites:
* Long Island Staylace Association
*sorry we do not allow links to commercial sites
Tons of articles, stories, pictures, etc. A great place to start if you need information.
* Vajsha's Corset Links http://vajsha.tripod.com/
Links to retailers, custom makers, articles, supplies for those who want to make their own, etc.
* Wasp Creations
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Probably America's top maker of quality custom corsets that stand up to the rigors of tightlacing. Amy (proprieter) has made some custom BDSM style corsets and has an interest in the lifestyle herself. Click the "Corset Articles" and "FAQ" menu options for some great general information about tightlacing.
Hope that helps!