If you're seasoning something like the deBuyer, GT's method is good. If you're doing it to cast iron, I would recommend a slightly different approach. Firstly, the type of oil you choose does matter. There's a bit of science here, and not just in regards to smoke point. Seasoning is caused by fat polymerization, and some oils lend themselves to this process better than others. Canola/grapeseed oil, avocado oil and flaxseed oil in ascending order of quality and price. You want a polyunsaturated drying oil high in fatty acids called ALAs. It's the release of the 'free radicals' that everyone whinges about when you heat an oil to smoke point that actually creates the hard, black and glossy surface. Simply put, the oil is heated, radicals are released and they bond to form the coating. Extremely bad for you when you're eating, but this is chemistry, not cooking. The most readily available and suitable oil is canola or grapeseed. It's cheap, and it's what I used. Avocado and flaxseed oil just have a higher percentage of ALA, so they make for a slightly harder polymer.
Stick your pan in the oven at 200 degrees. Let it heat for a while so the pores open. Take it out, and crank the oven to 350. While it heats, take your choice of oil and evenly distribute it across every surface of the pan. Then, take a paper towel and wipe it out. You want an extremely thin film of oil, it should be shiny but not visibly 'wet'. Your oven temperature must be above the smoke point of whatever oil you choose, but it doesn't have to be ridiculously so. Stick your pan in the oven, and come back in an hour. After an hour, turn off the heat, and leave the pan in the oven until it cools. When it comes out, it won't be glossy and black. It will be darker and increasingly matte in finish. Let it cool properly, and then repeat the process until you're satisfied with the outcome. Fair warning; the oil will stink out the house a bit, so open a window. After six bakes, my pans were both reasonably smooth and shiny black. Over time and repeated use, they've developed more of a shine and darkened in colour.
This is a fool-proof method for maximising the seasoning process. You don't need to go overboard like this, but I chose to do it to get the best possible result and it pays off. The more times you season, the harder your seasoning and the less likely it is to be stripped if you want to fry a tomato straight away. You could season it just once and away you go, but the more you do, the less it will stick. Might as well do it right the first time and never worry about it again.
