Try and get other web sites to link to your site, google will rank you higher for that.
If you have more than one domain such as .com and .co.uk dont have them linking to the index. have just say .co.uk link to index page. them .com to a splash screen which will then link to your main index.
watch using querystrings. They can trip up the google crawlers. there is software that can be installed on a web server which makes querystrings crawler friendly. If ther is anywhere in your site that could make a spider enter a loop tr and avoide this. To do so use a javascript link to that particular part of your site.
Use words that you have used in your keywords meta tag in places such as image alt tags-every little helps.
Also marking text up with tags such as <h1> and <b> boosts its relevancy from normal page text. So maybe put page titles in <h1>. But try and make sure only about 5% of text on each page is marked up.