Originally Posted by peter_d
What's the most important single piece of information you know that would help people new to SEO?
For on page SEO, first of all, if you don't have one already, it is best to have your ISP install the webalizer program:
on your site's server. This is a FREE program so your ISP should be able to install it very quickly. If they don't want to, then insist upon it. If they still don't, then move your site to a new ISP that will do this for you. Also have your ISP set the webalizer program to at least show 200+ search strings and 700+ total referrers. This should give you a good amount of very valuable and accurate traffic information about your site.
Also, IMHO, it is in your best interest to register an account at Google Webmaster Central:
and then verify your site(s) with Google and then install Google XML sitemaps. Also after making any significant changes to your site(s), then you should create news sitemaps, upload them to your site(s) and submit them to Google over and over again. Then soon afterwards you will receive more Google traffic information including keywords and phrases used to find your site(s).
After a month or so, using the Google traffic info and your webalizer info, then you should edit your site's front page and internal pages and include the search phrases and keywords from both Google and your webalizer. After editing your pages and uploading them to your server, you should run another Google sitemap and submit it to your Google webmaster's account once again. And this process of compiling your site(s) traffic data and accordingly editing your site pages meta tags is an ongoing process which will eventually increase your site(s) visibility and traffic overall. Yes, this involves a lot of repetitive work, but if you do this and do it well and consistently, in time you will see very good results.
Also, below is a very good article that I highly recommend:
Google Ranking Factors - SEO Checklist
Good luck to all!