Welcome to the Tricki – a Wikistyle site with a large store of useful mathematical problemsolving techniques. Some of these techniques are very general, while others concern particular subareas of mathematics. The idea behind all of them is to exposit techniques that are used regularly by mathematical problemsolvers, at every level of experience. We hope you will enjoy using and contributing to the site.
If you are new to the Tricki, you may find the following page useful; it has information about what the Tricki is, what its aims are, what we hope it will develop into, how to read, write, find, edit, or comment on articles, and more:
Update: Since MathOverflow really took off, the Tricki has no longer been under active development. Nevertheless, it still has a number of excellent articles, and so is being kept up so that these can still be accessed.
If you want to go straight to the articles, then you have several options. The best way to understand what these options are is to explore the following links. Clicking on the words "Quick description" will give you some information about what to expect from these links.

Different kinds of Tricki article
What kind of problem am I trying to solve? Quick description ( A list of links, each to a page about some general category of problem, such as "proving equality", or "classification" (which will itself consist mostly of links to articles lower in the Tricki hierarchy). )
Subjectarea front pages Quick description ( A list of links, each to a page about some area or subarea of mathematics. Although we are primarily interested in classifying articles by the type of problem they solve, it is in many cases natural to begin by restricting attention to the area they belong to. It is also desirable to have different ways of classifying articles, to maximize the chances that they can be found when written. )
General problemsolving tips Quick description ( A list of articles that give advice that can in principle apply to any mathematical problem. )
How to use mathematical concepts and statements Quick description ( You have heard of a definition or theorem, you know it is important because people say so, you know that people use it to solve problems, but to you it is a bit of a mystery how they use it to solve problems. If that is your situation, then this page is designed to help.)
There are other ways of finding articles. For more information, click on "Navigate" in the toolbar.
Regular maintenance: you may find that the Tricki is down for maintenance for up to an hour every Friday at 09:00 London time (GMT+0100).