By now we're all pretty much familiar with the grade school level skeletonized version of the scientific method. You form a hypothesis. You design an experiment that is all controlled so that you're only testing that one hypothesis. Then you repeat until you are...satisfied, I guess.
Of course the real application of science in the real world as done by real scientists is much much more complicated. Not every scientist at every step in their research follows all parts of the scientific method as it's outlined in textbooks. And the method itself is much more nuanced and intricate than you might like to believe.
But the heart of the scientific method is indeed the hypothesis. This is the fundamental basic building block of science. It's a guess about the way that nature works. And it's a guess that you're not exactly sure is right. It sits below the level of a full theory or thesis. It's an under-thesis...a hypothesis.
Of course no hypothesis sits on its own as an isolated island. Hypotheses are built from existing ideas and previous work. A full theory of nature has many intricate moving parts all supported and buttressed by many independent lines of evidence. Usually a new hypothesis sits on top of that framework or as a mild extension to that framework. It's very, very rare for a new hypothesis on the inner workings of nature to be spun entirely out of whole cloth.
But no matter what, a hypothesis must be tested. And not just once by one group with one method. No, the ideal is for a single hypothesis to be tested multiple times by multiple groups with multiple techniques. It's only through the slow accumulation of evidence and elimination of bias do we really accept our hypotheses as workable and elevated to the level of theory.
In our everyday lives we form hypotheses all the time. We're always trying to guess what other people are thinking or what they'll do or how something works. Many times we let these hypotheses simply go, or never bother running a proper experiment.
One of the most powerful lessons we can learn from science is that it can be applied to...not science. The concept of testing hypotheses isn't monopolized by scientists. We're allowed to adapt that technique into our everyday lives. Sure, we not may not have fancy laboratories or expensive telescopes, but we probably don't need those anyway to solve the kinds of problems we need to solve in our everyday lives.
Testing a hypothesis can be as simple as running a quick counterfactual idea. Assume the opposite is true - would you end up with the same result? Or you can even run a very basic experiment. Do your best to isolate the answer to the hypothesis and set up your controls and...see what happens. The most important part of this entire exercise is to be open to whatever the evidence says, because at the end of the day the evidence is the ultimate arbiter of our (scientific) decisions.