1) Craftsmen pay good money for their tools. Invest in your office space, whether its a dedicated space in your home or a coworking membership. But be honest about what tools you need. You probably don't need a $1000 aeron chair. But you do need one that's comfortable. You probably don't need that super-cool triple-panel 17" laptop Razer pumped at CES for web development. You probably do need something with enough RAM to run a few VMs sometimes.
2) Outsource everything that doesn't make you money or that you aren't good at. Taxes and bookkeeping, for example. But know enough about it so you can tell if you've hired good help there.
3) Invest in yourself. Learn some new technology at least once a year—whether thats a framework, a language, or a skill like design. Go to at least one regional conference, and at least one national conference if you can afford it.
4) Work the shit out of your network. Set a limit on how many unpaid lunch meetings you'll take to hear about other people's problems, and always try to find a way to help them even if you don't wind up taking the job. And then try to hit your limit most of the time. Farm favors like they're a cash crop.
5) Find a way to keep yourself accountable, whether that's a mentor, a coach, or an accountability partner. We all need someone to keep us honest about our motivations and rationalizations from time to time.
6) Try to exercise some self control over how many self-indulgent HN comments you make in a given period of time. :)