Keyword research is the first, and in my opinion the most important task in the search engine optimisation process, this is why you need as much data as possible on each keyword you are planning in implementing on your site.
First thing you need to know about a keyword is its search volume, the higher the better, Google Keywords Tool is showing local search volume now which is very useful for geo-targeted sites. Once you have the search volume you need to compare against the competition on that given keyword, here is a simple rule of thumb, higher search volume against low competition.
Ok, now you have the search volume and the competition of your keywords, but what if you wanted to know more about it, like how many sites are using your keywords on their title tags? For that you will need a special command when you perform a search just type intitle:keywordname to refine it use intitle:”keywordname” that will give an exact match.
What about how many sites have my keywords in their URLS? To find that out use inurl:keywordname again to refine it inurl:”keywordname”.
Want to know how many sites have your keywords in the anchor text of links point back to them? Use inanchor:keywordname and to find out how many sites use your keywords in their description tags use intext:keywordname
Always remember to refine results to an exact match just quote the term, this also works for a normal search query.
All these commands are very useful to tell how much competition a certain keyword has and to determine how hard it will be to rank for them.