A typical Tricki article will be an explanation of a technique for solving a class of mathematical problems. This class can range from the very specific (e.g. solving simultaneous linear equations) to the very general (e.g. the totality of all mathematical problems). Here are some examples of such articles.
Dimension arguments in combinatorics
We would like to keep the Tricki fairly focused on this core purpose. Nevertheless, it is perfectly reasonable to ask whether articles of a slightly different kind are permitted. (Of course, "permitted" really means "welcomed", since on a public site like this there is nothing to stop you writing any article you choose.) Here are four examples of other types of articles that one can imagine might be very useful.

Annotated bibliographies with links to articles in the mathematics arXiv.

Explanations of the history of, and motivation for, important definitions that look unguessable in advance.

Expositions of particular proofs that are clearer than any that can be found in the literature.

Articles about methods of proof that might be expected to work for certain problems but in fact do not.
We do not necessarily want to discourage the writing of such articles: our main priority is that the Tricki should be a very useful resource for mathematicians, and articles of this kind would clearly be useful. However, the Tricki is about methods for solving problems, so if you are considering writing an article, then try to keep it focused on that. For instance, an annotated bibliography of good textbooks for a first course in group theory is less welcome, but an annotated bibliography of textbooks that are particularly helpful if you find basic questions in group theory difficult is much more welcome. Similarly, if understanding the motivation for a definition helps you to use that definition to solve problems, then present it in that way. (For example, if you wanted to explain where the notion of cohomology comes from, then tell your readers how it can then be used.) In general we would discourage expositions of particular proofs, however enlightening, but that discouragement would turn to strong encouragement if the expositions contained ideas that could be used for other proofs, provided that this was presented as the main purpose of the article. As for articles about attempted proofs that don't work, these can shed important light on techniques that do, so it should be possible to fit such articles squarely into the standard Tricki framework. Perhaps the single principle that covers all these considerations is this: the purpose of the Tricki is to help people to do mathematics rather than to display mathematics to passive spectators.
It is possible that at some point in the future the Tricki might be broadened to encompass other kinds of articles about mathematics that do not have an obvious home in the conventional mathematical literature. If that were to happen, we would probably try to design the site in such a way that different kinds of articles were clearly differentiated from each other.
If you want to express a view about this or about any other aspect of the Tricki, there is a forum where such matters can be discussed. Contributions to this and suggestions for improvements to the site are very welcome.
How do I create a Tricki article?
How do I edit or comment on an existing article?
How do I make my article show up on searches?
What is the best way to make a suggestion about the site?
Why have a separate site rather than simply using Wikipedia?
Back to Tricki welcome page.