Personally, I use a combination of Google Adwords Keyword Tool, and a bit of common sense (of which I have very little ). For example, if I have a page about cats, you obviously don;t want to try and target the keyword "Cats". It's too general and getting ranked in the top 10 is near impossible without a TON of constant work. Then, if you do happen to get listed on the first page for the keyword Cats, you most likely will not remain there very long. Instead, think to yourself what keywords you woudl type if you were looking for a website about cats. Maybe you woudl type in "Tabby Cats", or "Calico Cats", maybe even "Fat Cats". Targeting 2 and 3 word keyphrases will greatly increase your chances of getting listed in the first page. There might be less searches for those keywords but, you'll get more traffic from those keyphrases by being on the first page than you would if you were on the 3rd page for a similar keyword. Good luck!
choosing keywords should be done carefully. when you are doing it manually you better concentrate on the words which are related to your site. the more your keyword relates your site the more you get visitors. effective keywords will help in increasing your site traffic. proper keywords to your site will help your site position improve. for eg. keyword like brainyquote will help in maintaining the site position for a site like www.brainyquote.com. make sure you enter your keyword in the title or some other place in your page. keep note on your competitors too. the more you get competition, you can more keywords. and of course key word tool too. more than doing it manually if you get assistance you will get more effective keywords. there are many keyword generation tools available now a days and i got it from Tucktail.com. they generate very good key word for my site.
