David Sacks, a former PayPal executive, has pursued several pet projects since leaving the online payment company in 2002. He produced the film Thank You for Smoking and launched Geni, a genealogy website. For that start-up, he created an internal communication system to help employees share information. He liked the tool so much, he spun it off into a new company called Yammer. These days, Yammer, which is based in San Francisco, employs more than 200 people. Its software is used by more than 100,000 organizations, including eBay, Thomson Reuters, 7-Eleven, and, of course, Yammer.

The way I work and the product I make are very integrated. I built Yammer because I wanted to work on a product that I would use all day. Does that mean I'm a workaholic? I don't know. I just know I want to use Yammer.

I check my e-mail first thing in the morning. If I get sucked in, I might still be in my boxers three hours later. If I can, I like to eat breakfast with my wife, Jacqueline, and my two daughters. They are 3 and 2. They're really cute, and I usually get home too late to see them in the evening.

I usually arrive to work around 10. Our office takes up the second and third floor of an industrial building in SoMa. The second floor is marketing and customer support. The third floor is sales, product development, and engineering. I have the corner office on both floors.

I have an open-door policy, and I've found that proximity matters. People are more likely to come see me if I'm nearby. So I spend Mondays, Wednesdays, and Fridays on the second floor, and Tuesdays and Thursdays on the third floor. I have a monitor in each office and carry my laptop back and forth.

I try to leave a lot of my time unstructured so that I can drill into whatever I think is most important that day. I like to manage by walking around—you get to see what's going on and interact in real time. People often have questions that I can answer immediately. And if someone is hitting a roadblock, I might save a month on the project just by walking over and asking, "How's everything going?"

When I'm in my office, Yammer is always up on my screen. If you just need to talk to one person, e-mail's fine. But Yammer allows you to share information with a lot of people and have a discussion about it. You can use it for status updates on projects or to ask a question or to post an interesting article that you think will be helpful. Basically, it's a place to share and get help.

Every team at the company has its own group in Yammer. I'm most interested in product design, sales, and customer support, so I'm constantly checking those groups.

Product design is my main focus. Everyone in our company uses Yammer, which is great, because you have better intuitions about a product that you yourself use. I designed the first version of Yammer myself, but as the company has grown, my direct supervision over the product has diminished. Now we have a dozen product managers and designers working on new features and upgrades.

In the past, I would walk around and look over the designers' shoulders to see what they were doing. I'm impatient. But I've been told that's jarring for some people. Now we have two scheduled product reviews a week. The product manager and designer present what they're working on, and I comment on it.

I check Twitter every day. I read every single tweet that mentions Yammer. I also get Google Alerts, so anytime somebody writes about us online, I read it. I want to know what people are saying, so I can keep improving the product and the company.

I'm in a perpetual state of frustration over the product. I want it to be perfect, and it's not. At least we can always make changes and progress toward that goal. One of the things I didn't like about the movie business was that once you lock the film, it's done. I can't really watch Thank You for Smoking, because I always see these little imperfections that I can't fix.

I meet with our sales managers at the beginning of each quarter. Sales is probably the area in which I've had to learn the most. Anyone can use Yammer for free. You just sign up and invite your co-workers. We offer premium features, such as integrating Yammer with a company's intranet, for a recurring fee. When we first started, I had this naive view that sales would just take care of itself—people would just pull out their company credit card and buy. But companies, especially large enterprises, like to talk to somebody. They've got concerns about security, privacy, and compliance. So you really need salespeople to engage with them. We didn't have any salespeople when we started. Now we have 30.

I do a few sales calls a week when one of the reps wants help closing a deal. I like to hear firsthand what customers want and what their objections are. If companies aren't buying premium upgrades, I need to know why. And that needs to be factored in to the product or the overall company strategy.

We do something called Yammer Time once a month. The whole company meets in the common area on the third floor. It lasts about an hour. Different department heads give presentations, or I talk about strategy. We also take questions from the crowd. People are usually interested in where the company is headed or what our competitors are doing. We also answer anonymous questions that come in via a third-party website. Those are often about money. We've had a few negative Nellies, but I don't mind criticisms. I believe dissent leads to consensus. I don't want to have a company where employees are afraid to say what they think. This meeting gets everyone on the same page and lets me address things that I didn't even know needed to be addressed.

I typically work pretty late. I have to make a special effort to make it home for dinner. I wish I were more disciplined. I don't have a set time that I go to bed or leave the office. I just do all the work that's in front of me, and then I look up and say, "Oh, wait, it's midnight; I should get home."

I try to save my weekends to spend with my kids. I usually spend the weekend doing things they will enjoy. Even though I don't go in to the office on the weekends, that doesn't mean I'm not thinking about work.

Disconnecting is very hard for me. I think about work constantly. I wish I had an On/Off switch. My wife is good at bringing it to my attention. We'll be at dinner or spending time with the kids, and she'll notice me tuning out. I'm trying to get better.

I don't believe in hobbies—if you are really passionate about something, it should be your job—but I do like to play poker. I play a couple of times a month. Phil Hellmuth is in my poker group. He's won the world championship and has 11 World Series of Poker bracelets. I'm not in the same league as he is, but I'm not a donkey.

Playing poker and running a start-up are similar in some ways. Mostly, you have to be comfortable with ambiguity. If you're the type who likes to very carefully weigh 99 percent of the data before you make a decision, you're not cut out to run a start-up. At best, you'll have 60 percent of the data. And you have to make a lot of your decisions based on intuition.