I really don't think that there's such a concept as too little. True, some "meta analyzers" say that I need more content in my meta keyword, but when really focusing on one keyword, I only list one, and that about it. True, used inside the page in different combinations, along with other words, but always the same form of the word. Too many? Whatever keyword you're not going to use frequently in your content is part of the "too many" group. FOCUS. That's the best thing you can do. Don't take the bots for stupid. I bet they "read" better than 80% of the globe's population.
Do you mean how many keywords to target your site towards? Or how many times to repeat a keywords on a page? For the first i think you should pick 3 or 4 main keywords to target (aim high be ambitious!!), then for your inner pages you are targeting xxxxxxx amount of keywords and phrases because nowadays blogs and sites can write about a whole range of things so sites rarley stick to one niche. For the second i think this would come naturally, just write your content towards a human and not towards a spider. Try and throw in the keywords natuarlly here and there of course!!
If you mean the use of keywords on your pages i would suggest that you want keywords to appear naturally.
If you're asking how many keywords should you target then I'd say as many as you possibly can. Continue to add pages that are geared toward different keyword combinations. Also, you should really evaluate your keywords to search results. What I mean is if you have a keyword that has a 200,000,000 results and people are only searching for it an average of 1,000 times a day versus a keyword that only has 90,000 results and people are searching for it an average of 500 times a day then the second example is a lot better keyword to target.
Where can I get that information? I've used google adwords suggestion tool but it only shows a bar for stats, no numbers.
I was just kind of using general numbers for the searches. You can use wordtracker which you have to take with a grain of salt. I should have said that you can kind of estimate the popularity of certain keywords in relation to other keywords and then target the ones that aren't as competitive when you factor in the number of results. I hope that clears it up.