Great Question, I'll add in my $.02 :)
I'm a 37yo that dropped out of college to go work during the late 90's in the .com boom.
I don't know what other people judge as 'successful', but a few things of note that has helped me make a great living and manage to get myself into positions of control and equity.
1. I'm always making sure that every hour I spend working is solving a BUSINESS problem, not a personal bauble that looks shinny and interesting.
2. Back to point one. I'm usually in a position where myself or the programmers on our team have a unique perspective into any project or business we are involved in. That said, I've become a quasi analyst with the business. I'm able to find 'leaks' in process and revenue that would be harder to find, and I'm always worth more around than to not be.
3. Try to keep your miracles to 2x a year. Bill Joy wrote that once, their aspen R&D team at Sun Microsystems are expected to perform them twice a year, and though not every miracle made it off the launch pad, a lot did.
4. Wins are found through empathy and inititive. Make friends, make yourself a hero by solving those friends problems and try to go out of your way to make the lives of the pople using your software easier.
5. Don't paint yourself into a box where you feel like you need to build 'fun' projects to be fulfilled. The most interesting projects I've done are often problems that people would fall asleep hearing about.
6. Get -very- good a picking horses. This is important! I've made a great living make sure that the people I work with and partner with are better than me. Always. I put myself in a situation knowing that if I don't go in with my A game, I'll probably not last long. I'm expected to do and build great things and often times I do.
That leads to...
7. Share your losses and your wins with the non-developers. When something is hard, and you solve it.. share it. When something is hard and you break it... share it. Communication is so important to building the only currency we have in our industry.. trust.
9. Only work on projects you -know- have the potential to make money. Never get stuck in the trap of being a 'cost center'. This is a dangerous place to be. Every project I've done and lived beyond 9 months is when I bled to make sure that the project is viable. Every project should be looked at as a individual P&L. consider what you make, what your team makes.. and make sure you're contributing to the bottom line revenue and health of the company.
10. Never be too good for anything, but also never get caught into the trap where you're doing anything that is below your pay-grade. This goes back to point 9.
11. Make your work your hobby, and your hobby your work. If you find real joy and meaning in what you do you'll have a great career regardless of the financial rewards.
12. Never ever spend time away from the core of the problem. Be close to the guys talking to the customers, or the vendors depending on your model. Understand their pain points, their concerns. It will help you understand how the software you're building is effecting the human-side of the equation. -NEVER- isolate yourself away from what we call distractions. Be apart of the chaos of a new business, you need to understand exactly what's going on so you can head problems before they become a crisis and an emergency.
That said. I've been involved at a partner level at various companies over the years. One we had a big hit that we sold to a international corp and though i didn't leave and buy an island, it offered me the ability to pick my subsequent projects very carefully. Any startup I'm in I'm sure that I'll at least own a good-sized chunk of the company in equity. I spend a lot of time working to understand what would be the best use of sparse technical resources and development to gain the most buck.
Any time we as a team start looking on how to attack code, we all ask ourselves... "Where is the business win?" We try to test all of our assumptions on priorities and features against that. It keeps the true scope of what we're trying to do in line, and can really add urgency when it might of been less obvious.
I've worked with a couple of partners over the years that have proven to have the right chemistry. I'm careful to not commit to things I don't believe we can do with success. If I don't think our team can effectively guide the project to success, we don't do it. If we do commit to it, we'll drive to a POC as quickly as possible and start iterating through feedback as quickly as we can.
We are engineers, we're not wage-earners. The experience we have solving software problems often puts us in a position to solve business problems with the same pragmatism.
Seek to make impact. As a matter of fact, try to be an impact-whore. In business I've seldom seem much else matter.
As someone else in this thread said, you can be a wage-earner or figure out how to participate in the business. By doing the later, I've been able to exceed what I believe my peer-wage earnings by many times. Don't be scared of that side.
No point in human history has so much new business and revenue been possible with just the trade-off of energy of the building of something new. I've been a part of a new start-up that started sadly enough in my basement. We operated like that for about 3 months before we felt we could justify the office space. We brought on people very slowly, and though now we're moving forward at a little more exciting pace, we were profitable at month 2 with 5 employees including myself and a few other not-so-expensive people.
The joy is, as the business continues to grow, I'll participate on the upside of it.. and one good month can be worth more than a year of salaried work. You taste that 1 time and it's like crack, it's hard to go back to being just a wage earner.