Well in my opinion, I'd concentrate on having proper keyword phrases in your title tag, in at least 1 H1 tag within the body tag and within at least one sentance/paragraph of text on all pages.

You could use different keyword phrases targetting a different one for each page, further increasing your opportunities with the big SE.

As to meta tags. As they are primarily ignored by the big SE, I'd not spend a great deal of time on those, but they are nice to have, keeping them short and succiinct... say limited to around 15 or so. More than that is really just a waste of effort in my opinion.

Same deal with the description meta tag.

As to the alt tag on your images, don't overdo it either.. won't really help all that much.

While Yahoo seems to enjoy spammy pages, Google is still top dog and they don't, so I'd go for a balance and be careful of over doing the keyword density in the content.

Again just my opinion.

hth
Ian