Here's a bit more information about the TKT, from my notes on last week's seminar. There are three modules to the exam, which can be taken in any order. Each module is one hour and twenty minutes long, and comprises eighty questions. This means you're answering one question per minute. It's objectively assessed, so all questions are multiple choice, one-to-one matching or odd one out. Grading is on a banded basis, and consists of four bands, one being the lowest and four being the highest.
Module One covers aspects such as defining terms, identifying learner needs and presentation techniques. It's broken down into three parts: describing language and language skills (40 questions), background to language learning (15 questions), and background to language teaching (25 questions). The TKT glossary is very useful for the first area, whereas the others can be researched from a variety of sources, of which The TKT Course from Cambridge University Press and The Teaching Knowledge Test from McGraw-Hill are a couple of examples. However, the knowledge a teacher has accumulated in the classroom is also invaluable for this exam.
If you would like more information about this test, I have found the TKT Handbook to be very useful. It includes more detailed information than I've given here, as well as practice tests and an answer key for those who wish to take the self-access route.