"Lean" has become a very popular buzzword to describe processes in startups and in larger companies, and while many people expect it to mean that a company spends very little money, that's not it. (Those people are thinking of bootstrapping.)
Lean is a methodology (really a set of methodologies) the basic premise of which is that the success of any product or business is contingent on certain assumptions, and that those assumptions can be tested in fast, cheap ways. So instead of simply running with your business idea and waiting to see whether it succeeds or fails, you can identify the important assumptions and test them, using that information to either Persevere, Pivot, or Perish.
<aside> ☝ If you remember the scientific method from high school, we're basically applying that to the process of starting a business
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If you've already created a Vision for your venture, that vision hinges on some assumptions. The most basic one is "I believe people want my product/service" but there might be more nuance around things like how much people are willing to pay, what features they desire, the types of channels they'll use, etc. Before you can test your assumptions, you need a pretty comprehensive list of what they are.
Once you know what your assumptions are, you'll rank them by their importance to your startup's success (or failure). The most important one is the first one that you'll want to test, because it has the highest probability of sinking you if you've gotten it wrong.
Tests come in lots of shapes and sizes, and there are some great resources out there to help you decide what tests you should use. (Here's a link to a book that I was recommended.) One of the more common tests is the Minimum Viable Product. Depending on what it is you're trying to find out about your venture, different tests will be more or less relevant. The important part of test development is determining what you'll measure, and setting your thresholds for what will be a "success" or "failure."
<aside> 💥 Try to avoid making your goals too easy or your testing criteria too vague. A test disproving your assumption isn't a bad thing! It's a much easier way to learn than going to the market with a faulty vision.
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When the results of your test come back, assuming it's been well-designed and well-run, you should have data that either confirms or refutes your assumptions. Based on that information, you should either:
Running your company as a lean startup is really the ultimate in Validation because as we discussed back in the entrepreneurial process, validation doesn't stop once you're in the market and selling. Good companies are constantly hypothesizing, testing, and adjusting.