Hi,
is there a way to find out which are the most common key words used to search something in particular sphere. To be more precise for instance I want to find out which are the most common words used by people, looking for job and examples of job interviews.

Wordtracker can give you a search count for your chosen key phrase. It also provides alternative phrases related to the one you chose. There is a free trial available for you to try it out.

I've also heard good things about keyword discovery.

you may do a search for "free keyword suggestion" in any search engine.
one such free tool i refer to is in digitalpoint.com

try overture or wordtracker, they provide alternate keyword.

lamemaster:

Try the 'Google AdWords Keyword Tool'. It's a free service that allows you to get a good idea of how popular a keyword is. Play around with it, I think you'll be satisfied with the results.

You can use keyword suggestion tool at Digital Point and also have a look at keyworddiscovery.

Just a quick question: How many keywords is too much?

*nevermind: I figured out myself*

You can find your information regarding popular search engine keywords at these places:

Overture keyword tool or buzz.yahoo.com - for yahoo

for MSN - imagine-msn.com/insider/

Google - google.com/press/zeitgeist.html

Hope that helps a little.

Check the Overture tool out it is free and useful. You can almost multilply the results by 4 t 7 x to estimate Google traffic - tah's what I've found anyway.
http://inventory.overture.com/d/sear...ry/suggestion/