To many, kata is the ultimate demonstration of karate as an art form. It is the opportunity to demonstrate your understanding of the underlying principles of each technique, whilst also displaying mastery over your own body and the forces of gravity. However, you should always remember that the kata must be functional - if the moves are not capable of protecting you, then you're doing them wrong!
Back in olden China, students used to practice counters in response to set attacks. Current theory has it that martial practitioners reduced all hand-to-hand combat to just 36 possible attacks, with 107 variations. They then devised responses to each of these attacks. Different martial systems offered different responses, and in order not to forget the various responses and counters, they were grouped into the sequences we now call kata. The sequences were never really intended to represent a single, continuous fight, rather they represent a series of short set-pieces.
Kata function on two levels; the superficial level of blocks, stances and counters, as practiced in most modern karate styles, including GKR; and a deeper, hidden level of pressure point strikes, joint locks and deadly accupressure techniques. This deeper level was passed on from master to student only when the master considered the student worthy. Unfortunately, it seems that some masters never found worthy students, and so the deeper meanings have been lost. Even where the techniques have been passed down continuously, word of mouth is a notoriously unreliable means of preserving information, and changes have crept in as each person interprets the kata for his or herself.
Having said that, many experts consider that kata should represent a personal performance interpretation, in which the practitioner adapts the moves to his own physiology and capabilities. Thus, a tall person may block with greater speed, whilst a shorter person may instead use greater strength. Each person performs exactly the same moves, but the moves are personalised.
Although many of the moves within a kata can be employed for different purposes: to block a low punch, or a high kick for example, the original kata were intended to block specific attacks. Perhaps the world's foremost researcher into kata bunkai (meanings) is Canadian-born Patrick McCarthy, an award winning author who now resides in Australia. He frequently tours in Australia, Britain and America, and if you wish to learn more about the deeper meaning of kata (not specifically GKR kata), his open seminars are highly recomended.
If you wish to explore the origins and intent of kata further, I suggest that you visit The International Ryukyu Karatejutsu Research Society.
As your grade increases, don't think that you can forget about previous kata. Your performance of first kata, or saifa, or whatever, will still help to determine whether or not you deserve to pass higher gradings and receive your next belt.
In GKR, we have a saying, "To get your black belt, you'll need to perform a black belt first kata". In other words, whatever your grade, you'll need to perform each of the kata you know, at the level appropriate to that grade. A black belt does first kata better than a red belt, and a blue belt does it better than an orange. It's a neverending process of improveent and refinement.
Although kata is not performed with actual opponents, always bear in mind the fact that you are simulating serious, sometimes even life and death battles. Perform the moves with power and/or speed where appropriate.
By far the most common mistake made in all kata is improperly performed stances. I would suggest that setting your foot angles correctly to the nearest micro-degree is less important than where your weight is positioned, whether your knees are bent or locked, the position of your hips, and the strength of your stance. However, your sensei may think differently, so if you have doubts, discuss it with him or her, then follow their instructions.
A well performed kata is technically accurate of course, but it also demonstrates power, focus and a variation in pace according to the moves being performed.
To see kata performed as they should be, speak to your local sensei who will be able to supply instructional DVDs of all the kata up to Empi. The videos are mostly narrated by Kancho Robert Sullivan and performed by Shihan Stacey Karetsian.
Beyond Hangetsu, you will be taught new kata personally by your sensei when he or she feels the time is right for you.
Above all else, remember the key to great kata is the same as the key to great karate - practice, practice, practice!