Welcome to the forum, Snuggs!

here is a list of useful codes you can use in your posts. It should deal with spoilers, formatting and the like.

As for signatures...well, they appear in all the posts you make, so you can use them to have links to useful things quickly on display for people (mine, for instance, has a link to my pbp registry entry, for potential GMs of mine, then a link to the guide to pbp that people may find useful, and then another link to some avatars made that are up to adoption, in case someone wants them). Also, you can use it to share quotes or pictures that you really like. It's another way to be recognized, bascally.