Before you start building your website you need to know what your customers seek on the Internet. There is no reason to focus on phrases that no one seeks or on phrases with a very strong competition. The key to your success is finding the ratio (KEI) between frequently searched terms against the least number of pages where they can be found.
With this tool you can calculate which keywords are the best for you.
The whole process consists of 3 easy steps:
1. [Searches] - Explore relevant keywords using Google AdWords (Global Monthly Search Volume)
2. [Results] - Check the current index of documents for each of them in Google
3. [Keyword] - Choose the keyword that you like and press "Calculate"!