I follow a few different methods in combination to get an ebony black pan/wok in an hour or so. I picked these methods up in "Breath of a Wok", an essential book for people cooking with Cast Iron or Carbon Steel (in my humble opinion that is).
1. Scrub the heck out of it with mild soap, steel pad, and hot water.
2. Place over screaming high heat and let it open up for a good 10min or so. It may smoke some too as anything remaining burns off.
3. Add a couple cups of salt to the pan and scrub the pan with it over high heat until the salt turns dark and the pan begins to change in appearance.
4. Let the pan cool off & discard the salt.
5. Wipe the inside of the pan with canola oil and heat over high heat until it smokes and blackens.
6. Wash the pan out with water and a brush (no soap!). Wipe dry and wipe the inside with a papertowel dampened with canola oil.
7. Repeat steps 5 & 6 until you have a slick black coating on the pan surface.
8. Fry some minced green onions in the oil and from hence forth clean the pan as described in step 6.
Nick ~ "Egg whites are good for a lot of things; lemon meringue pie, angel food cake, and clogging up radiators." - MacGyver