I have two main 13" skillets that I use on a daily basis. I love to cook with them. I found one and bought the other. One is a Lodge and the other a no-name. Both are equally good, but I prefer the no-name one. I re-season them when food starts sticking.
Anyhow, to re-season my pans, I get them hot on the stove with some water in them. Then, I use steel wool (I use fine) and go to work on it, taking off a good bit of the black. I rinse well with hot water and then repeat the process.
Next, I get it hot again on the stove (a good 5 min) to be sure there is no water left on the pan. Then, I cut off the heat and put on a HEAVY coat of Crisco and put that in the oven at 250 for about 15 min.
After 15 min, I pull out the skillet (use a mitt) and pour the excess oil out of the pan into the sink. Then it goes back in the oven at 280-300 for 2 hours.
This is a long process, and you can repeat the crisco and oven treatment 2 or more times if you want. The more times, the longer and better the non-stick effect will be. Let it cool down between each treatment.
Finally, everyone's grandmother has a different method for seasoning a pan. I've tried a few, but find this to be the most sure fire way to make it happen without the risk of burning the oil.