Think "specific keyword phrases" not "keywords". Why? Due to the extreme amount of competition for general terms in the search engines, if your keyword phrases are too general it is very unlikely you will rank well in the search engines. You stand a far better chance to rank well for specific phrases where there is less competition. The resulting traffic, since it is more highly targeted, should also be much higher quality too.

1.


Try to think like your target audience. What would they search for when looking for the page you are optimizing? It is very easy to fall in the trap of coming up with a short list of what YOU would search for, but what about everyone else? They will not necessarily use the same keywords as you. You should try to come up with as many keyword phrases as you can think of that relate to the page you are optimizing. Try asking a few friends and family what they would search for when searching for a site like yours.
2.

Check out your competition for ideas. Do a search using keywords that you already know you want to target and click through on the top sites that come up. Once on the site view the source HTML code and view the keywords they have in their meta tags - this should give you many more ideas! Make sure to only use keywords that relate to YOUR site or page. To view the HTML code simply click the 'View' at the top of your web browser then select 'Source', or 'Page Source'.
3. You should develop a list of keyword phrases, following the tips on this page, for each page that you optimize for the search engines.