When you first start homebrewing, every batch is an exploration. You build a knowledge base of processes and ingredients by executing other people’s recipes. That experience later helps you start making your own modifications. It’s an organic kind of learning.
Eventually, you look back and realize how much you know, but there’s always more to learn. As a seasoned brewer, it might be time to augment your casual approach with something more structured. It could start with something as simple as trying out a new technique on an old, reliable recipe. If you want to get more serious, you can bring in some rigor and apply a version of the scientific method by focusing on a brewing element, making a testable hypothesis, trying it out, and then assessing the data (i.e. the beer).
What is the Question?
The first step is to pick your target: what are you trying to evaluate? You want to control the scope of your investigation. This is a matter of trimming away distractions to get to the root. Choose something specific, such as asking what first wort hopping does for a beer or wondering how fermentation temperature impacts the phenol/ester balance in a wheat beer. Constraining the question provides the structure for your experiment.