SEO stands for Search Engine Optimization. This is the process of optimizing your website to get as high a ranking as possible for your key phrases in search engines, thus bringing you hundreds, even thousands, of targeted visitors’ everyday. People are forever arguing about the algorithms search engines use to rank sites, but in my experience, the highest amount of relevant inbound links will rank top. By relevant I mean links with anchor text related to the search. So if a search is made for ‘fishing’ and you have 10 million links to your site, all with the anchor text ‘fishing’, you will rank number 1!
Maximum optimization comes when it's thought about before the site is even developed. Before you start creating content you want to make sure you have a market available. To do this quickly you can use a FREE tool called Web CEO. It helps to do maximum work with minimum effort. Research your keywords and find out how much competition you have for them and how many daily word searches there are for them. Along with this you can use it to manage your PPC campaigns, find your ranking on as many search engines as you want, for what ever key phrase you want and lots lots more! For a better tool (which costs money), and the one I use myself, have a look at the link below.
A lot of experts are argueing over this factor and have been for a while. My take on it is that it is probabaly more important in some engines than it is in others. I don't think it's so important in google however and that is what i try to optimize for. A good domain name, being relative to your sites content, is helpful though if you want people to remember your name and come back. Being catchy also helps.
Everything written in your site should be there for a reason. Babbling on is pointless. Every single word should be there for a reason. For your content to be considered useful by a robot you need to have a keyword density over 4% but at the same time you don't really want it over 15% as this may look suspicious. If your writing relevant content about your subject this will usually just occur naturally, but tweaking it is something i would recommend for maximum optimization.
Directories are useful in two ways. First of all they independantly act as another place for visitors to find your site, but they also act as a place for search engines to find your site. This helps with your popularity. Some directories are free but some you have to pay for. I would reccommend signing up to lots of free ones but also paying for related ones, but make sure you find a good package! A lot of the directories are partnered so try to find an offer where you can get listing on say 50 for around $200. Also check the directories PR. Do not pay for a directory listing if you will be on a page with PR4 or less.
There a few to get you started but make sure you find ones relevant to your site and submit to as many as you can. They can easily be found by searching '(your subject) directory' into any major seach engine. Please note that directory listings and links to your site are vital for search engine optimization!
You can do this manually which is very time consuming or you can pay for software to do it for you :) Submitting itself is obviously a good idea, instead of waiting for search engines to find you, you find them and let them know you're there.
If you want more information on SEO then i would reccommend reading Brad Callen's SEO Made Easy. It's completely free but packed with invaluable information that anybody can understand. You don't have to decipher the technical terms as you browse through.
As a webmaster you will have lots of things to be concerned about, and SEO is very time consuming. Here is a quality company that will do all the leg work for you: http://www.abalone.ca/