John O’Farrell never meant to stay in the United States—originally from Ireland, he came for an MBA at Stanford in 1984, intending to return to Europe right afterwards. “But I fell in love with the place,” he says. “Who doesn’t fall in love with Silicon Valley?”

He joined Andreessen Horowitz as the third general partner because he felt it was a different kind of venture firm, made up of operators rather than lifelong investors.

“We set out to build and operate businesses,” he says. “We came late to venture capital, and really tried to build the kind of venture firm we would’ve liked to have.”

He was originally an engineer, and in the early days of his career worked for some huge companies, such as Siemens in Germany. “I never set out to be a VC,” he says. “I don’t know that anyone says at the age of 5 or 6, ‘Mom, I want to be a venture capitalist.’”

 After his MBA, he gradually moved from larger companies (Booz Allen Hamilton, Telecom Ireland, US WEST) to smaller, high-growth startups. He worked at @Home Network—“It was a dot-com poster child, the first company to invent and bring to the consumer high-speed Internet,” he recalls. “Back then, we thought 14Kb per second telephone modems were revolutionary.”

He then went to Loudcloud, which was founded by Marc Andreessen and Ben Horowitz, as one of the first companies to offer cloud computing and software as a service. “We went through the mother of all recessions and nearly went out of business, but managed through a series of complex transactions, acquisitions, and a lot of hard work, turn it into Opsware,” he says. Opsware sold to HP in 2007, and John went on to Silver Spring Networks, a Smart Grid company focused on consumer electricity.

With his years of operating experience under his belt, he joined Andreessen Horowitz in 2010, and started blogging in order to help entrepreneurs avoid the mistakes that he and his partners have made in the past (“They get to make new mistakes,” he says.)

He gets inspiration from a variety of sources, from advising companies who want to do business in other countries, to buying two cars for his triplets who just reached driving age. “It’s easy to write fast, it’s hard to write well,” he says. “I’m challenging myself and getting input from others on relevance constantly.”

He particularly likes blogging about international expansion and going global—he is, after all, an Irish man who went to school in Germany and married a Brazilian woman. “It’s a favorite topic of mine and it’s a hard thing for companies to get right, because most of the entrepreneurs are doing it for the first time,” he says. “I’ve seen a lot of bad experiences there, so that’s my focus.”

He never thought he would be involved in entrepreneurship, because of his upbringing. “Ireland is very conservative, or was when I was growing up. It had gone through hundreds of years of being a colony of Britain, famine, rebellions, poverty…Risk-taking was frowned upon,” he says. “Every successful family would have a priest, a doctor, a lawyer, a policeman—entrepreneurs were unheard of.” His parents even sent him and his five siblings to Germany for schooling, so that they could gain another perspective.

He offers three pieces of advice for up-and-coming entrepreneurs: 1) “Make sure you pick a big enough market. The number one reason we turn down companies is we think the market is too small”; 2) “Avoid business model innovations just for the sake of it”; and 3) “Take your time. Increasingly you have the luxury of time, because it’s not that expensive to start a company anymore.”