A few things I've learned since becoming my own boss. Please add yours!
  1. Learn to treat your time as valuable.
    When your time is divided between office time and non-office time, as in most traditional jobs, it's easy to keep track of your billable hours. But when you don't have an office (or at least not one with a boss who is keeping track of your whereabouts), it's important to be intentional about how you spend your time. Time really is money, which brings me to my next point...
  2. Don't give your time away for free.
    When someone asks to "pick your brain," or asks you to work on their project as a favor, they are asking you to work for free. If they are not a charity you want to support, or a friend you genuinely want to help out, you must either decline or charge them money. It was hard, but learning how to do this made all the difference for me, both financially and in terms of my self-respect. Read this: http://onforb.es/1PJP6bB
  3. If it makes sense, get representation.
    Agents and managers of all sorts can help you get work and broker deals. At the very least, find a good lawyer who can help you with any contract you sign.
  4. Create a schedule and stick to it.
    Include exercise, meal breaks, errands, and of course, worktime and deadlines. Having a schedule, even when there's nowhere you *really* need to be helps keep you on track.
  5. Don't say yes to everything.
    At first, it may be a good idea to say yes to most paid projects, but it's important to trust your gut when something feels like it might not be a good idea.
  6. Don't be afraid to follow up with clients about money they owe you.
    I have sent more emails then I am happy about to billing departments reminding them about money they owed me, sometimes for projects completed several months prior. It's awkward at first, but eventually you remember, "hey, this is my livelihood."
  7. Take advantage of your flexible schedule!
    Some of the best parts of being your own boss: you can go to the gym in the middle of the day when nobody's there, you can take conference calls in your pajamas at 4 PM, you can decide to work from the beach, and you can go grocery shopping when the stores are virtually empty!
  8. My wife likes to say "Create an arc to your day."
    Suggested by @zkamenetz
  9. Negotiate money and don't be afraid to ask for more.
    Negotiating money is the hardest part. Be clear as to what the expectations are and why you are charging the client the amount. I like to break it down into line items so client really understands where the money is going. Equipment $XX. Time $XX. Writing $XX. Social promotion $XX. That sort of thing. And if you are in the middle of the project and the client asks you to do MORE than you had agreed on tell him/her you're happy to do it if you have time – but it will cost more.
    Suggested by @eatthelove
  10. Offset your own overtime
    I travel a lot for work and often work a long day on a shoot so now I schedule a down morning or full day to offset that extra time. I treat it like booked client time so I'm not tempted to email or do a "little favor" etc.
    Suggested by @laure
  11. Get really fucking good at what you do
    Suggested by @kavutskiy