Altars are a very important part of the magickal process. They provide a working space as well as a visual focus. Your altar can be any shape you wish, but round is traditional (due to the meaning behind the circle). Any size works as well, as long as it's large enough to hold what you need while you work, and not too large to allow you enough room to work around it comfortably. Wood is also traditionally used, but feel free to use whatever works (even a TV tray, provided you never use it for anything else again). What the altar itself looks like is up to your own personal preference, so be creative and find something that you feel comfortable working with.