SEO is very important, because without high rankings you're in trouble, of course unless you find a niche with less then 50 people searching for it a month.
Here is some of the things that search engines will rank your website after.
Inbound links: both the number and the quality of your inbound links counts, and here is what i mean about quality and number, quality is because search engines will see a link from a site they trust as more important then a link from some link farm, and the number is important because the more quality links you have the better you will rank.
a link from a site such as EzineArticles is very high quality, where as some link from a random directory is very low quality.
It is better to have your link in the body then it is having it in a comment: if you're doing linkbuilding with blogs, then try to e-mail the blog owner to get him to write an article about your business, instead of trying to get a link from a comment on he's blog.
Please try to avoid link farms (also called free for all pages) the way to spot a link farm is when you find a site that has thousands of links on it and not a whole lot of inbound links because these sites may do more damage then good to your site.
Onsite factors that matters: H1-H6 titles.
these are important because Google will rank all the keywords in your body text after importance, meaning that if Google visits your site it will attribute the most importance to your H1 keywords.
A clever title: you should always try to find a clever title, lets say that you sell shoes on your website, Now a wrong title would be shoes and a clever title would be shoes for you.
Make the best urls, for your website: A wrong url would look like this Randomcompany.
com/4554566464545454.
html While a good url would look like this Randomcompany.
com/we-have-the-best-shoes.
html.
You should always keep your landing page from different searches as close to your root, on your webserver as possible.