hey SMS - you should definitely be trying to move away from (by the sounds of it) a badly templated site. Pages should have a clearly defined hierarchy (as previously mentioned.)
Taking the link from wmmc above and looking at some of the top tips, imagine you have a page about your driving school. Using the good domain, good url, good keywords, good description, good hierarchy tips it might look like
Domain/URL www.shreksdrivingschool.com/about_shreks_driving_school
title : About Shreks driving school
Keywords : Shreks driving school, driving lessons, driving lessons in the swamp
Description : Need to learn to drive in a swamp? Shreks driving school is number 1 in the swamp.
h1About Shreks driving school - (should match the page title)
h2 Why are we different
Learning to drive in a swamp is never easy. Here at Shreks driving school blah, blah, blah, blah ,etc
h2 History
We've been teaching gnomes,princesses,dwarves and other magical creatures to drive safely and avoid accidents with swamp donkeys since 1999. Blah, blah, blah, blah blah
Obviously you might want to replace blah, blah, blah with better words but you should get the idea.
H1 and Title tag content should match - H1 and Title are essentially the same as the headline in a newspaper/magazine. Sub-headings are defined by h2,h3,h4,etc. Content should have relevance to the title, keywords should have high relevance to the content and title etc. The more you can tie the elements together, the more relevant a page will appear.
Take heed of the last link LL posted - avoid using 'Click here' links - link the words that relate to the page you're linking - even better if they match the title of the page they're linking to.
Don't use images without ALT tags - search engines don't see images - they DO see the ALT tags. Make the alt tags descriptive relevant to the page .
As the article suggests at the end, SEO doesn't just depend on page structure, following rules, etc! If you could nail SEO google etc would just have to break it again in order to make money (everyone can't appear at number 1 in the results for the same query).
Using classes to define styles that are externalised into a stylesheet is a good idea. Styles are exactly that though - they define style NOT hierarchy/importance.
hope some of that made some sense. wmmc, please correct any mistakes if I've said something glaringly wrong!
One thing you should be doing is using something like Google analytics to see who is coming to your site, what they're looking at, how long they're staying etc. That way you can look at improving your content/page structure/links etc.
With GA, you'll be able to see what search terms lead people to your site. That might give you the confidenc.e to start using adSense
Got to run..