When I was 8 or 9, I started using bulletin board systems, which was the precursor to the Internet, where you'd dial into... a shared system and shared computers. I've had an email address since the late '80s, when I was 8 or 9 years old, and then I got on the Internet in '93 when it was first starting out.

Be careful not to start a company that really belongs as a feature of another company, like the 25 Twitter URL shortener companies out there. Pick a real problem that's here to stay.

It's okay to doubt yourself, it's okay to feel down; just never give up.

I wanted a personal-finance tool for people who didn't want to be accountants: something you could set up in ten minutes and spend less than five minutes a week on. Mint is now that tool.

In the first three years of Mint, from when it was founded to when it was sold, I can honestly say that in a sustainable way, I couldn't have worked any harder on it.

I have always thought of myself as an inventor first and foremost. An engineer. An entrepreneur. In that order. I never thought of myself as an employee. But my first jobs as an adult were as an employee: at IBM, and then at my first start-up.

Before Mint.com, I was a long-time user of 'Microsoft Money' and Intuit's 'Quicken.' Both were powerful tools, loaded with features and functionality around taxes, investment, budgeting -- too feature-laden, in fact. They took hours to set up, forever to learn, and an hour a week to maintain.

You don't start a company because you want to be an entrepreneur or the fame and glory that comes along with it. You become an entrepreneur, and you create a company to solve a real problem. And by real problem, I mean a problem that is going to exist down the line.

Tell your idea to whomever will listen, and you'll get valuable market feedback before writing a single line of code.

At Mint, we developed five pending patents on our technology, ranging from categorization to the Ways to Save system that calculates how much a new financial product would save a user given their present financial situation.

Mint is designed to put your finances on auto-pilot. Whether you log in or not, it will send you a weekly summary of your balances and biggest purchases, and how your investments and budgets are doing, along with sending you alerts on unusual spending and low balances.

I actually don't invest in anything that is social, mobile, deals or ad networks simply because those are areas where there are so many players and so many other smart people in the space, I feel like I don't have a competitive advantage. So I tend to go after things that are e-commerce, like healthcare.

I always knew I wanted to be a technologist, so I went to Duke and got a degree in computer science and electrical engineering. Really, I thought my goal in life was to be an inventor, a problem solver, so I thought I needed a Ph.D. to be good at inventions, but it turns out that you don't.

If you look on Amazon -- if you do a search for personal finance, there are literally 20,000 books written on personal finance, and there's no real reason for it. I mean, personal finance is pretty simple.

I consider myself an inventor first and an entrepreneur second. In real life, my hero is Thomas Edison. He was a great inventor, but also an outstanding entrepreneur who was able to sell his inventions to the masses. He didn't just develop the light bulb; he invented the entire electric grid and power distribution system.

At 16, I started a web development business and had clients from the Netherlands, Caribbean, and across the country -- none of whom knew my age because I could conduct all my business with a phone, scanner, and the Internet.

Carefully calculate the potential size of your market to make sure you can grow. Before starting Mint, I knew that there were about 20 million people who had purchased 'Quicken' or 'Microsoft Money' over the years, and 80 million people using online banking in the U.S. alone.

I pitch Mint to everyone from investors to engineers, young and old, and I do it pretty much the same way: Here's the problem in the market place, here's how we solve it, and here's how we make money.

The other big factor in building trust quickly is site design quality. Mint.com has one of the best graphic designers ever (Jason Putorti) -- he cares about every pixel, all the fonts, all the transparencies and effects. And that shows instantly. People do make judgments of trust on appearance -- in the real world and online.

One third of the economy goes through 'QuickBooks' in terms of businesses invoicing other businesses. Each invoice contains a connection between vendors, suppliers, and customers, and also the price of that connection. Representing the payment graph is huge opportunity and something no other company can do.