You'll need to do tons of research.
1/ You polish your manuscript, rewrite it and edit it until you couldn't possibly make it more perfect. Then you look for reputable agent who are interested in your genre. You query them and follow their formatting preferences. If they like your book, they will contact you. Your read the contract, make sure it's what you want and you keep going.
2/ Yes, all authors first time or otherwise get paid royalties. But what they get at first is an advance on royalties. Meaning if you get a contract with an advance of 5000$ and royalties of X%, if your book sells over 5000$ worth of royalties, you'll start getting extra money once you've earned back the 5000$. If however your book sells less than 5000$, well you just keep that but you won't get anymore (of course not since your book isn't selling). A lawyer is involved if you consult one to read the contract for you. Get one that knows publishing contracts.
3/ Almost any book can claim to be a best seller. There's no official requirements to be allowed to use the bestseller label. So you need to check out exactly what list the book is a best seller on. Being a best seller in the local store at Nowhere Town just means you've sold the most copy in that shop that week. Being an Amazon best seller can mean you've sold the most copies in the last 10 minutes. Being a New York Times best seller is a much bigger deal. It means you've sold the most books nationally that week. But making an appearance once on that list is not the same as being best seller of the year or staying on their weekly list for weeks and weeks.
I suggest you go lurk on Absolute Write and read pretty much everything they say about publishing. It takes time, but publishing is a real business and you wouldn't open a restaurant without checking the market first.
EDIT: regarding copyright, there are a lot of myths out there. The reality is actually extremely simple and convenient. People aren't really out to steal your book because it's not a lucrative business.. You'd have to be extremely lucky to find the one book that's gonna make money, even luckier to get it published, even luckier to get it to sell. The people who might be able to recognize the next HP (agents, editors, publishers) would go out of business if they tried it. Not worth the time and effort or the lawsuit that follows.
And if you were one of the very few unlucky people to whom it happens, you are automatically protected by the Berne Convention which states you own copyright as soon as you've set pen to paper. You don't need a "proof copy" whatever that means. If it ever goes to court, the simplest way you'll determine your book is yours is that it was published first. If it happens your book was somehow stolen before publication, all you need is your drafts and/or your saved computer file. You should have plenty of these. You can also show that the thief had access to your work (ie they're your former roommate back when you wrote your book or that agent was queried in 2001 but rejected your manuscript and now he had it published without a contract with you.) Chances of that happening are next to zero.
Myths: sending it to yourself and not opening the envelope. It doesn't prove anything. I can send myself twenty open envelopes today, then wait 20 years, print best seller books, put them in the envelopes, close them and say "see I wrote them 20 years ago".
Red ink - I have no idea where the heck anybody got that one, but printing in red ink does not copyright your work.
Disclaimers: writing "that work is mine and I'll sue your pants off if you steal it" on the first page doesn't do anything more than the Berne Convention does except making you look stupid. Published books have them merely for references on when the copyright was registered (in the US, the publishers registers the copyright for you usually. registration is not necessary to avail of copyright. Elsewhere, no registration is done. The copyright information is dated from first publication).
Slapping on the copyright logo: unnecessary. Your work is protected. Having Cs everywhere doesn't give any extra protection. It just makes you look silly.