The value of a tag should be viewed in light of a tag’s purpose. There are really two types of “tags,” according to some, though we usually call only one of them the tag.
(1) The bold statement above a quotation that summarizes the quotation.
(2) An oral statement in the round that summarizes your point/what you are about to prove.
Our experience has taught us that the best system is one that does not view both scenarios as utilizing the same tag. In other words, what is down on paper as the “tag” will not be the “statement” or “summary” of your argument. There are some good reasons for this:
When you are in a round, people cannot usually flow an entire sentence, so a long tag is not very useful. You want your statements in the round to be short and “flowable:” illegal immigrants harm wages, OR wet foot/dry foot is unjust, etc…
But when you have a huge brief with lots of pieces of evidence, you might have TEN pieces of evidence that can all be used to show that illegal immigrants harm wages. So in your brief, you want tags to have a little more detail so you can distinguish between these ten pieces and pick the one you need. Tags in a brief should be more like a sentence: illegal immigrants harm wages because they are willing to work for less than Americans, OR wet foot/dry foot is unjust because it discriminates on the basis of ethnicity, etc…
So far, then, a “good tag” provides some details for why a conclusion is reached. This helps you find the right piece of evidence that you’ll use in the round, then you’ll state your own “summary” of the argument you are making in the round–but you won’t read word-for-word the tag from the brief (which is more boring anyhow).
Besides making the right pieces of evidence more easily procurable, a good tag should accurately reflect the quotation. The tag should NOT reflect the argument you can make by using the quotation, but rather reflect the actual quotation itself. This should be self-evident, but often is overlooked: mis-representing the quote and making your argument as the tag is usually called “powertagging.”
Powertagging it not useful because you usually know what argument you’re trying to make and you need to quickly find evidence that will say what your tag says. It is pretty embarassing to see people read a tag straight from someone else’s brief or a sourcebook and then the evidence says nothing of the kind. Interestingly, you could probably have reasoned your way to the conclusion of the tag after the quotation, but claiming that the quotation actually says your conclusion when it doesn’t greatly harms your credibility (and provides a niche for good sourcebooks to compete ;-)).
So a “good tag” is one that accurately summarizes the quotation and provides some details for why the conclusion is reached.