Added: Zeroth Set.
The subtle arts of definition.
Briefly, put all of your concepts into explicit words so your mind can't accidentally slip without noticing.
To think at all one must have thoughts. The thoughts have some nature, which defines and is defined by the thoughts. Untrained thoughts equivocate and conflate. First gain awareness of the definition of your own thoughts. Know them exactly.
Definition can be prescriptive or descriptive. However, in either case, you must first apply an arbitrary label.
If you wish to think upon an external phenomenon, the definition is not up to you. It is a description of what's already there. Take an example of the event and label it with your favourite term, then identify all other events that are in the same category and list their properties. You now have a label-category association, which is what a definition is. Check a few extra examples to ensure the boundaries of the category are where they're supposed to be. They won't be, so fix the definition and check again.
Unfortunately once you have a coherent term which doesn't include random detritus or fail to include obvious specimens, it will no longer match the folk definition. Perhaps swap out your favourite term for something more apt, because it has become jargon, and using the original as jargon is predictably confusing. In any case, the label isn't important. What's important is understanding the category. Call it skoobarg if you want, as long as you understand what it means.
If you wish to think upon an internal idea, the definition is wholly arbitrary; however, the logical consequences of the definition are not. You get to attach any non-contradictory set of properties together, and label it with whatever you want. However, you then must list at least a few example of real-world events that fit in the category.
Look particularly for advents that aren't supposed to fit, such as Diogenes' chicken. The logic is implacable. You must either bite the bullet or change the definition. What is included is not up to you; to change the category you must change the logic which means changing the definition. Getting a coherent definition to cover the events you want it to cover tends to be impossible; settle for good enough. A coherent definition is far more important than your personal aesthetic hangups.
A category can be quickly tested for coherence by using the "all X are Y" form. E.g. all fire is hot. We can choose the boundaries of the category "fire" in many ways, but if we start including cold fire or wet fire, we have an incoherent category; we fucked up the definition.
If you define justice descriptively, you may (will) find that what is usually called justice is unjust. It constantly makes unprincipled exceptions and is wildly unfair. Whatever justice is, it certainly can't be the opposite of blind.
Internally I use one (nonverbal) word for thing-which-is-called justice, and another for Just justice.
Prescriptively, I define a just society as one where cooperation is high status and defection is low status.
Most disagree, because the human status instinct inherently applies the highest status to those who defect and get away with it. Women are attracted to criminals (who aren't for-real schedule for execution).
However, my definition results in just societies becoming richer and unjust societies decaying and collapsing. The natural definition results in unjust societies becoming richer and just societies decaying and collapsing. These observations are in fact identical. However, it seems that calling health and welfare "injustice" is intended to mislead. Almost as if everyone knows that telling the truth about high-status individuals would force them to stop defecting.
Arguing about "free will" is almost fully political.
If you have a precise definition, the answer is trivial. Busywork. Is it hot? Then it's fire. Is it cold? Then it's not fire. If you don't have a precise definition, the answer is impossible. If you forget what "hot" or "cold" mean, it gets rather difficult to work out whether something is fire or not.
These arguments are about the downstream meaning of "free will" which is again either trivial busywork or intractable. Typically the arguments are intended to disguise the fact that the disputants already know the answer; they're both trying to get the other to forget something important so they can pull a scam.
Secure your shit. Define your terms.