I would recommend reading through the SeriousEats link another user posted. They dispel a number of old wives tales and incorrect information. Soap and water work fine, and won't damage the seasoning on a well cared for pan. The user who mentioned running water over a screaming hot pan is asking for the pan to crack. Deglazing can help, but that's a lot lower stress on the metal.
As for seasoning, I like to cook a bunch of bacon. If you ever cook large pieces of beef or pork and end up trimming the fat, you can render these trimmings in your pan to add another layer. A number of online sources suggest Flax oil as the best of the best to season a new fresh pan with, but ultimately, you're creating a polymer layer on the iron and most fats with decent smoke point temperatures will work well (i.e. you probably shouldn't use olive oil)