Not really. Most comic book writers don’t have agents and if they do its not for comic book work- its for regular book publishing and for Hollywood.
If you want to bring your work to an established publisher you need an “in” with an established publisher. You need for them to have a reason to look at your pitch/work.
A personal relationship, an established body of work, a favor, etc. Otherwise, they aren’t going to bother looking at what you have. They don’t have time to look at some stranger’s idea.
Some companies, like Oni press, just did a few months of open submissions to help broaden the pool of creators, but that is pretty rare.
If you have an original idea (meaning your story isn’t “the best Batman story ever!”) and you’ve never done a comic before, unless you are VERY lucky, your best bet is to self-publish. It is insanely easy in this day and age to do it… you just need money to pay an artist–that is your biggest cost…and art is expensive.
Any publisher is more apt to listen to you and your idea if you can hand them a physical piece of work *…a completed piece of work. It shows you can actually do the thing, instead of just having an idea for the thing. (*or a link to your webcomic site or a pdf)
And as Chuck said… no one is going to steal your work…and if they do (either knowingly or unknowingly), I pray you had more than just one story in you. Comics is a small community and people will usually know if something nefarious went down. At conventions, being afraid of someone “stealing my idea” has to be one of the biggest excuses you hear from people as to why they never started or finished a thing.
Format…it’s pretty similar to screenplay and most screenwriting software will have a comics template available. Essentially, you describe what the still image is in each panel and give as much or as little detail as needed–but each artist/writer relationship is different.
My first comic experience taught me a great lesson- the artist is not in my head. The publisher got the art back and sent to me and said “Um, can you rewrite your script to match the art?” It was awful–not the art itself, but it was clear the artist did not understand my story and time was short so I had to basically do it old school Marvel style which is dialogue-ing and captioning around the art.
My next book, went much much better.
You can also PM if you have questions you want to ask off board.