I do not think in terms of keywords, more of key phrases. For Instance, in the link at the bottom of my sig, my anchor text is "Free Digital Stock Art Photographs To Download Or To Be Framed". It is one keyword phrase, which contains a bunch of keyword variations. There is no limit to how many of those you can have on your site, just do not spam it, as you can be penalized. So, to answer your question, I utilize about 300 keyword phrases on my site. (Organic, not PPC)
i believe that you can target as many keywords as you can, but don't place it in one phrase that jdw4jesus said.. for instance, you have a product, and each product has its own page, promote that page individually with its product keywords..
I have a site where I promote hundreds of keywords and they all rank in or near the top 10. I think a practical limit would be about 100 keywords per area of your website (pages that interlink to each other). Each area of your website should be backed up with inbound links on that topic. Varied to match your keywords (and their synonyms and related phrases). Google promotes sites based on how the keywords relate to each other and how well the inbound links (and the sites they are on) agree with your page content and title tags.
My present 5 campaigns through YSM are being promoted with 50,000 words each. But it can get very tiring going through and rehashing them from time to time. I wish there was a script that could do this for a person.
don't get keywords and make the content awkward to get the keywords in it create the content and then work your keywords into that that's the way to do it
You are right about the keyword targeting. But you also have to make content that is relevant to bring the traffic with those keywords or phrases. A good percentage is content for keywords at around 5-8%. Anything more than that will tank your site. A good tool to use for your phrases or download Googles Editor.
In terms of quantity, the number of keywords you want to target highly depends on your website. If you website deals with Digital cameras, you might want to optimise your website for: - A couple of generic terms - Specific brand terms - geogrphic terms In the end, you can have 1000 of keywords. The number of keywords you want to optimise your website for also depends on your time and budget... You can optimise for as many as you want, but it will be a lot of work...
The more you target them more work you must do. Its up to you to decide how many and how much time you got to do it.