Hi Jeroen – when choosing the right keywords for your Adwords campaign, there are 2 critical components to review:  1) search volume and 2) keyword competitiveness.  In the past, you had to use tools such as WordTracker, etc…  however, Google Adwords keyword tool is now updated to show both of these variables, all in one spot.  Let me quickly give an overview of these to critical variables, and how to use them in tandem when choosing keyword phrases for your Google Adwords campaign:

1)  Search Volume:  enter in a list of keyword phrases you are considering for your campaigs, and then click on the “volume” heading so that you sort the list of suggested phrases from highest to lowest

2)  Competition:  This indicator is now extremely powerful since you are comparing the competition to actual search volume data.

The objective here is to find high volume search phrases relevant to your campaign’s objective, and the identify low comparative competition for those high volume searches.  This is where a lot of opportunity can be found as far as maximizing your ROI, quality score, etc…

This is a brief suggestion, but one that if you get in the habit of using, you’ll become very good at judging the numbers and analyzing the results.