keywords in Title but how much ?

[cagliostro]

Hello and thanks for all the usefull posts in this forum. I read it all.

I own and run a dynamic website for specific classifieds. For two years now, using adsense.

While it has grown in means of traffic, it is not enough to make some real monthly money.

So reading here i realized that i THOUGHT my site is SEOed. It is but i'm not targeting anything, just providing "honest" page titles.

So now i have done my work and have a list with keywords and phrases that pay well and have medium competition. All that stuff...

The question is how much i should add them to the pages. And where.

For example i have 20 main categories with goods. Then i have tones of subcategories in them. And last i have the Classified post itself.

Should i put the words in the first two, all three ?

I have no idea.

thanks