This really depends on what your trying to achieve with your site when you designed and developed your concept. you could have a really niche focused site aiming to rank for 1-3 keywords or you could be thinking about a larger site with many keywords on a subject. To answer this question you need to think about what your objective for the site is?
You can target 2 or 3 primary keywords per page but apart form this do not forget to incorporate long tail keywords and primary keywords modifiers.
Hi, Target not multiple keywords for the site. two, three keywords for the site which have good traffic and searches in search engine.
I would recommend focussed keywords as suggested previously and usually use approximately 4-6 depending on niche. Some seo tools recommend you have less than 8-10 keywords max.
It totally depends on your practice if you have less time to taget keywords so you can target 3-4 keywords. If your time frame is long so you can increase keywords according to your SEO practice.
There is no clear instructions about how keywords you must to use. All depends on your goals and ideas. In general the term of density the keywords exists, but I think it's very conditionally.
2 - 3 keywords per page if the keywords are spins of the same main keywords. If you try to add to many to a page all you are doing is watering down the keyword richness of the page content.