A point of interest to most members of this list - at Yahoo, you may submit to two categories. Choose your categories before you begin, then submit as your primary category the one that is least crowded. For example, you may live in Zambia and have a web site about telecommunications. But telecoms in Zambia is something special, so submit to a regional category first, then choose a broader telecoms category second. For the true search engines, you should think carefully about structure and choice of words.
Strong content is just as important, so get that first.
Your page title should be descriptive. The first thing that loads should be a paragraph thta summarises, in plain language with keywords, what the web site is all about. That will be enough to get you indexed properly. When it comes to ranking sites for queries, both the directories and search engines have their own methods, and very few outsiders know what they are. Concentrate on the content of your web site, not on what search engines think of it.