I started writing when I was about 8 years old, took a about a decade off in my 40s-50s because I was stupid, and started again seriously a few years ago.

I started writing at an early age too. Our teacher wanted us to write a story for class credit--anything we wanted to write. I was hooked instantly :)

Right now, there are not many really big horror publishers. Nightshade and Leisure have folded. Cohesion is showing a lot of promise and Dark Regions is excellent, but doesn't have open submissions very often. Permuted is a good sized organization. Perpetual Motion Machine and Omnium Gatherum are really starting to pick up steam and have both had Stoker nominations with them this year. There aren't really as many mass market horror paperbacks hitting the shelves from non big five presses as there used to be. You'll find most horror books hit Amazon instead of finding shelf space, except in better, independently run bookstores. Deadite Press does wonderful things, Keene, Edward Lee, Wrath James White and sometime in 2015, myself. Horror publishing is not going to get you on grocery store shelves anymore, which is all right. There are still lots of small to midsized options doing wonderful work.

Neverending's advice is spot on, but yeah, Samhain is badass. I would not recommend querying Cemetery Dance for anything until you've got a serious reputation. Mostly, I'd advise you join Duotrope to learn about markets and go on Facebook and friend or follow writers you like.