Which tool do you use to determine the competition for a given keyword?

Newbie here. I'm trying to learn about the art of keyword researching and would like to know about the tools you guys generally use to find how hard the competition on first few pages. I know that manual check is part of the process but an automated tool would come in use to separate wheat from the chaff.

Thanks.

Nothing works better than the brain. I also use SEOquake seo toolbar: http://www.seoquake.com/

Although it entirely depends in the nature of keywords & type of competition you want to analyze; to analyze advertisers competition, Google Keyword Planner still works best for me.

I use Google Adwords obviously it is best and from searches you can check the competition,very simple I guess.