I started a publishing company recently. We are just at the beginning of it, so I can't speak as to the success of it yet. But here's a few lessons learned:
1. Don't quit your day job. Don't put all your eggs in one basket. Don't burn any bridges. You are taking a risk on starting a new business, and even if you're really, really excited about it, it may not take off. If you have no contingency plan for failure, then there can be some serious consequences such as bankruptcy, getting sued, and so on. Likewise, don't quit your job just because your business is successful. A few months later you may be back, begging for a job. My advice is simply, don't be stupid about it. Plan for success, but assume failure - that way if you're successful, then great, but if you fail, it's not the end of the world.
2. If you're working with other people (i.e. it's not just you), make specific plans. Create a company notebook or wiki or something for everyone to reference, and have specific, step-by-step instructions for how to deal with finances, how to deal with technology (logins, etc.), how and who pays bills, etc. If it needs to happen, make a plan and an assignment for it so that you're not constantly behind on bills, your website, setting up your email system, etc.
3. You have to birddog things. Since it's your company, you have to keep pushing until you get what you want. You care about your company, but other people don't. If you want it to happen, you have to keep pursuing things until they DO happen, not just quit when someone tells you "no".
4. Have a business and marketing plan. Take some business and marketing classes, and a financial class or two (or just hire a CPA if you can afford to). Learn how business works and how marketing works. No one will know about your product if you don't do marketing.
5. Get really organized. REALLY organized. You need to be able to find anything at a moment's notice. I recommend adopting David Allen's "Getting Things Done" system. Ignore the bloggers who constantly blog about it instead of doing it - his stock system is good, just read the book or get the audiobook, setup the system, and start doing it. He has the best approach to organization I've ever come across.