Hi,
I want to insert the keywords used in google (via adwords) to include in my landing page. Is this a good idea? If so, how do I do this? I tried this plugin for Wordpress : http://keywordinsertionplugin.com/ . But I don't get it working.
Thanks
Yes, it's a good idea 
Google loves relevance, because users' love relevance. The more you can put the keyword in the ad text, then on the landing page, the better your campaign will do. Also, Google will bold the keyword in the ad text, leading to better CTR.
Add me on Skype, RingPartnerMike, and I'll share a script we use to pre-pop the keyword to the lander.
I think you can just grab them from the GET request if you're inserting the {keyword} dynamic token into your Adwords URLs.
You'd just do <?php echo $_GET['keyword']; ?> to echo them on a PHP page.
Thanks Ringpartner and Caurmen! Tried allready code from Caurmen and this is working smooth! thanks. Ringpartner added you skype, would like to see your code as well!