Ev Williams is about to join the billionaire club.

His 12 percent stake in Twitter makes him the company's largest shareholder, and according to the just-released S-1 filing, that stake will be worth $1.2 billion when Twitter goes public.

I spoke with Williams earlier this year when he was featured on the cover of Inc.'s February issue on the rules for success. At the time, he said his rule is "do less," reflecting on the focus and restraint he and his fellow Twitter co-founders showed in the company's earliest days. Much of that interview was left on the cutting room floor. Here's an extended version:

On focusing the idea:

"There are certain businesses that you know what they are when they're born. You don't necessarily know how big they are or what's going to make them successful, but Google, for example, was always a search engine.

With Twitter, it wasn't clear what it was. They called it a social network, they called it microblogging, but it was hard to define, because it didn't replace anything. There was this path of discovery with something like that, where over time you figure out what it is. Twitter actually changed from what we thought it was in the beginning, which we described as status updates and a social utility. It is that, in part, but the insight we eventually came to was Twitter was really more of an information network than it is a social network. That led to all kinds of design decisions, such as the inclusion of search and hashtags and the way retweets work. All this came because we were thinking deeply about the question: what is the essence of this product? It didn't reveal itself immediately and would have been a lot harder to get to had we not been focused on that."

On features that never were:

"Any time you're building a product, there are a million things you want to add to make it better, but the fact is the vast majority of them will not impact your success. It's more important to make those decisions well than it is to figure out how to increase productivity so you can add more and more.

Twitter's an example of this. Over the first year or two, we took away almost as many features as we added. We were sure we needed to add features for Twitter to make sense for a larger audience beyond the geeks that were using it at the time. We ended up never adding them. Whether or not they'd be good additions is hard to say, but clearly they weren't required for success. The No. 1 requested feature by users in the first year or two of Twitter was some way to group your Tweets, sort of like Google Circles. Users were dying for it. We thought it'd lead to a bunch of growth, and we were talking about it in 2006 and just never got around to it. It arguably would have been really bad, because it added complexity that wasn't necessary."

On starting slow:

"At Twitter, we had this mindset that we were going to do lots of different things. We probably would have moved on before there was any evidence of success. It didn't take off right away, and many of the most important things don't take off right away, they only take off after working on them for a long time and pursuing a vision that gets you to the essence of something, which is often only boiled down after lots of hard work and noodling on something... and maybe having doubts about it."