Great info on this topic!
Now, my 
ON THE POSITIVE SIDE
REDUCE YOUR KEYWORDS per page! The more focused, and symantically similar the page is, the more likely it will receive favorable indexing from Google (and the others). For example, i would reduce my keywords to 10 per page and have them be as similar but different as possible. When optimizing for a city - and a specific service, its more tricky to do. You will find it difficult to rank well with one site offering plumbing services to 50 different cities.
Good example of meta keywords: "pets,dogs,cats,turtles,fish,leashes,food,grooming ,vet,shots".
The first keyword "pets" should be the most saturated keyword on the page, dogs the 2nd most and so on down the line. Be sure to use these words and know phrases (i.e. "dogs" and 'mans best friend") in the body of the page. You should strive to a minimum of 300 words in body text. You will also want to put your #1 keyword in an Hx tag, but be careful not to overuse. Also, boold, underline & italics are great ways to add emphasis to a particular keyword in the body text.
I would not bother with ALT tags.. as they are not used by google.. but if you ALT tagged every image with the same tag - it could hurt you.
Make sure that your keywords to non-keywords ratio is at least 5 or 6 to 1. But never less than 20 to 1. Make sure your top keyword(s) are in the title tag, and the URL route (see posts above). Be sure to include KEYWORDS in the text linking that goes to other pages.
ON THE NEGATIVE SIDE...
STAY AWAY FROM LINK FARMS. While back-linking is still very important, do not share links with link farms or FFA's in any way.
DO NOT use immediate re-directs.
DO NOT use ANY duplicate copy. DO NOT COPY from any other sites.
DO NOT use SINGLE PIXEL links
Thats all for now, dont want to entirely give away the farm...
