In theory, the principle of optimizing your web site for the search engines is very simple.
What you want to do, is to have keywords on your site, that match the keywords that people type in on the search engines.
The search engines will crawl the content on your site and send you searchers that will find what you have on your site relevant to what the searchers are looking for.
It's as simple as that, in theory.
Where it gets tricky is in the execution.
For instance, how do you get the search engines to crawl your site in the first place? How do you know what people are typing into the search engines to find your site? For the record, the programs that search engines send out to "crawl" the web are called "spiders.
" Get it? Geek humor...
moving right along...
Keyword research will tell you what people are typing into the search engines to find you.
Having said that, here are 5 things that you can do to aid your optimization efforts and to attract the search engine spiders to your website.

1. Social media optimization/ sites.
   What this entails, is going on to the different social media sites and creating a profile with content that is relevant to your niche.
   Social media sites like MySpace, Facebook, Hi5, etc.
   can, depending on their individual terms of service, provide you with both links back to your sites and an audience for your content that will then go back to your site.
   Be mindful of spamming the site, since spamming can get you banned.
   
2. Social bookmarking.
   This entails creating links back to your site from places like stumbleupon, digg, reddit, furl, etc.
   On these sites, other users will put links to your content, provided your content is interesting/ good enough.
   Traffic from these sites can come in spikes and can be unreliable and some sites have different rules for how the content comes in to the network, so "your mileage may vary.
   " Like before, don't be spammy and you should be ok.
   
3. Distribute videos.
   Like with the previous sites, videos can get both people and search engines to come to your site.
   Make sure the video is high quality and provides some kind of value to the viewer.
   Try to make sure that your video is related to the content on your site, and don't be spammy.
   
4. Distribute pictures.
   Like with video, pictures on picture sites can get both people and search engines to your site.
   Like with video, you want to have quality photographs and of course make sure that you own the rights to whatever photos you distribute.
   
5. Link building campaign using our targeted keywords.
   All of your links should use your keywords.
   Some of the above sites will allow text links, some will not.
   Regardless, you want to make sure to review the terms for the sites to make sure that you do not run afoul of the guidelines.
   

Is my point about not being spammy getting across? No one likes web spam, don't be known as "that one spammer" if you can at all avoid it.
Bonus: Forums.
Sometimes, in some niches, web forums can provide you with a lot of visitors and targeted customers.
Please make sure that you participate and provide value to the forum members before you try to sell the members anything.
Make super sure that you familiarize yourself with the forum rules before joining and/ or posting to any forum.
Bonus #2: Articles and article marketing.
Writing and distributing articles is a great way to both show off your knowledge and get people/ search engines to come back to your site.
There are many different article marketing sites, each with their own submission rules and guidelines.
Make sure that you familiarize yourself with the rules before your submit content.