There are many traits and habits that successful entrepreneurs, especially repeat ones, display. Most of them are correlated to, but don’t directly cause success. And so they’re typically not necessary, nor sufficient conditions, to being or even becoming an exceptional Founder. Many common ones are public: charismatic leadership, having a sales-oriented approach, or being strategic about delegating. But there’s one which I’ve noticed that typically goes unnoticed, not because it should be private, but because it’s personal. Many successful entrepreneurs keep a running list.

The list is usually one of the two key raw ingredients to starting a company: a list of ideas or a list of people. Some founders actually keep two lists, one of both categories. Of course, they’re in all sorts of formats. Some are raw txt files formed in TextEdit/Notepad, some are in Excel or in Sheets or in Evernote, and some are literally written on a running piece of paper. The other week I talked to one serial entrepreneur who kept multiple lists in differing electronic and physical formats in various places, and had been meaning to consolidate, but liked the fact that he always had a venue to jot down his ideas wherever and whenever they were conceived.

Despite the fact that ideas are ephemeral, replicable, and some would say they’re “cheap,” ideas are indeed the keystone for forming and creating a new company. Behind each idea is an implicit hypothesis about the world today and what it could become. The concept behind a company contains assumptions about how people behave and what could make their lives better. A running list of company ideas is not just a way to enumerate business conceptualizations, but to test and refine them, by ranking and prioritizing, by riffing on and editing. A running list of startup ideas isn’t a static document, but rather a living one in which the stronger potential ventures rise to the top.

The other running list type I’ve heard more than a few times is much more tactical: a list of people who could be early team-members of a new company. If startups are really about aggregating talent and ideas are fungible, these building blocks of human capital create the structural foundation for a new venture to endure. A record of not just who is in a Founder’s orbit, but who could be an integral co-Founder, peer/partner, or early team member. Because the right idea can change, so can the right teammate which matches the business. Having the right DNA in a company at the formation stages sets up the trajectory from the start.

For some entrepreneurs, these lists aren’t kept physically and literally, but are rather mental annotations. Regardless of their origin, ideas and people coming together to start a new company is best when it’s the result of deliberate planning and architecting. Great Founders are always keeping tabs on the what and who for their next startup, because the right time of “when” could be soon.