If you are looking for serious, meaningful, organic search engine traffic, you simply need to do the following in the same order, depending on your circumstances.
Depending on your website, you may want to start from scratch again if you are in a competitive area or niche.
Get a good grip of your keywords for you particular niche, this is very important and will affect your results if you target the wrong keywords.
Next, get a damn good domain name, the older the better, preferably with some page rank or at least some back links.
The domain name should be in your specific field or niche area, the more relevant the better. Make sure it does not have a Google penalty in effect.
Next, make sure you get your website up as quickly as possible and start name you pages closely to you main target keywords, target one keyword per page if you can.
When using one page to target a keyword, the most import factor is the page title and the relevancy of the content on the page.
Target as many keywords as you can, go for the long trail. For S.E.O, get as many content pages on you website as you can.
You should have a number of main pages where you have your best content on and lots of other pages being added on a regular basis, with lots of interlinking between pages.
The single most important factor to your S.E.O campaign is the number of quality back links you can get back to your website. Also get links to your internal pages.
The best way to build your back links is slowly and steadily. Its crucial that you get your anchor text within links just right. Using the formula here will reap dividends for your S.E.O campaign.
Use a number of different combinations for you back link text, you will need to make them look as natural as possible.
Search engines place a lot more value of links coming from sites in the same category as yours, or sites in related areas or similar niches.
As a minimum you should try to get links that are related or semi related to you niche.
It also helps if you can get the widest and most varied I.P address and domains from where your get your back links originate from.
If all the above is done properly, you will get a healthy amount of traffic. You can try to do it all your self, or life can made a lot easier if you hire a quality S.E.O, who should already be using the above steps for results.