How do you know your criterion is good? It'd better be--after all, debates often hinge on the criterion clash.
Here are six simple questions that may not have simple answers. Use them when developing your case, to ensure that your criterion is useful, valid, and defensible. You might also use these questions (or variants) in C/X to set up attacks on your opponent's criterion, or to determine where the criterion debate should go. (I owe the wording of #s 1-6 to a former CHS debater who won't be named unless he really needs the ego boost. The explanations are my own.)
1. Is the criterion defined?
A "rookie mistake" is to simply put a criterion out there, as if it magically defines itself, or, even more magically, everyone agrees on the definition. Consider a common criterion: utilitarianism. If you (or your opponent) say, "Utilitarianism should weigh the round, because we have to judge moral actions by their consequences," you've missed a step. Fundamentally, utilitarianism considers consequences in terms of the greatest good for the greatest number. However, that's not even far enough: there are several shades of utilitarianism, including act utility (weighing consequences of each action) and rule utility (weighing consequences of a moral rule). If, in cross-examination, your opponent can't distinguish the two, then you have grounds to toss out their criterion and the judge should adopt yours.
2. What falls under the criterion? What is its "bright line?"
Consider utilitarianism. Does it account for agency? In other words, could we use it to judge the actions of robots or animals or hurricanes? Must one be a fully rational agent to successfully implement a utilitarian moral calculus? Is utility positively or negatively defined--in other words, by benefits conferred, or by harms reduced? Or both?
Also, what is the bright line in utilitarianism between a bad action and a good one? How does one measure "goodness?" Is it good enough to have a majority of 50.00001%?
3. Does the criterion weigh both sides of the resolution?
If you are operating on the assumption that the criterion is a moral philosophy by which we compare values, or weigh arguments, then this question is essential. A criterion that links to only one side doesn't help a judge use it to weigh the round. It acts instead like a second value or a sub-value, or a precondition to "fulfilling the value." That's okay in some judges' estimations, but at least to me, it makes deciding the round awkward--it forces me to develop my own bright line to compare case structures and arguments.
If you ask yourself, "How would my opponent win my criterion," and you find yourself thinking, there's just no way, then you have a criterion that works for only your side. Will that work for your judge? That's an open question.
4. How does the criterion link to the value?
Consider a value of justice (defined as fairness) and a criterion of utilitarianism (defined as the greatest good for the greatest number). Is it fair to give the greatest good to the greatest number, or is it fair to give a moderate amount of goodness to everyone, or neither, or something else entirely? You must make the link. You cannot assume your judge will make it for you.
5. Is the criterion universal, or at least widely accepted?
Let's go back to utilitarianism, just to be consistent. Do many or most cultures agree that goodness for the greatest number is a valid form of moral decision-making? Or is it inherently masculine, heterosexist, ethnocentric, racist, or limited in any other potentially debilitating fashion?
6. Is the criterion generally good?
Nihilism might be clever and make a great case, but most people find it intuitively disturbing or unsettling, creating an artificially high burden of proof should you adopt it. The same goes for other out-there stances that are unfamiliar--they often require so much explanation that the work of affirming or negating the resolution is pushed to the fringe.
On the other hand, it's fun to learn about new philosophies and moral theories, and it's fun to introduce them to others. It can also throw your opponent off track. Use your best judgment.
7. Do I understand the criterion?
For your case, it's essential that you can defend and develop arguments relating to and consistent with your criterion. Have your peers or your coach walk you through potential C/X minefields before running it at a tournament. General rule: if you're not sure how to pronounce it, stay away.
In C/X, if you don't understand a criterion, chances are your opponent doesn't either. Have your opponent explain it and re-explain it or give examples of applying it until you're either satisfied with the explanation, or sure that your opponent is blowing smoke.
8. Can I explain the criterion in one sentence or less?
This helps with #7. If it takes a paragraph or a page to put into words, you might be lugging a forty-pound broadsword into battle when you really need a dagger. (Or insert your own less nerdy metaphor here.)
Have other good (general) questions about criteria? Add them in the comments. Or, trash these ones, and explain why my analysis is flawed. You're a debater, after all.