As already mentioned, there are a lot of video tutorials out there that go over the basic steps. Watch them, figure out the basic steps and if you have any specific questions post it here and I'll help out, but honestly if I had to write a guide to 360s in text, it would be a few thousand words long at least since it's a very complicated topic.
Just keep in mind that spinning isn't one technique, it's several techniques put together at the same time (Pop + carving + Rotation + switch riding for those 180s) with a specific timing to when you have to do each skill and how you combine them, which is why it's so complicated and tricky to learn.
But yeah... lots of free trick tip videos out there that will go over the basics and you can come back here and ask if you need more detail on a specific area and I can break that down for you.
Oh and just one other thing I'd highly recommend.
Learn it on flat ground first. You can perfect and learn the entire 180 and 360 technique on flat ground first, then take it to jumps and small side hits afterwards. Spinning is mostly about timing each of the individual techniques to work together at the right time and by learning on green runs first you can keep working on that timing and try it 100+ times in a row with very low risk.
(edit - totally forgot I made this awhile ago. Here's a page of a ton of spinning tips I've written in the past: http://snomie.com/ultimate-guide-lea...owboard-spins/
I've got a lot of free guides and content planned for the forum too, just been too busy to implement them - but hopefully I can get around to it soon, just need to find the time.)