i am new - how do i check unique searches?

though i am not new to this buisness i was using up until now my gut feelings when deciding to promote any new ideas (and i am doing very well).
yet i need to cut my efforts. so... how do i check the amount of searches per period of time and what else should i consider?

thanks

Google keyword tool

Yer you should be useing google analytics for tracking visits and pageviews etc