I have a landing page in which I need to understand what keywords are coming in from AdWords and then display some information based on this. I am not certain, but I don't believe that this information is in the request header the same as normal query keywords would be. How can you ascertain this information and properly strip out the inbound AdWords keywords so as to use meaningfully?
If by keywords, you mean what the user searched for, that's possible.
Look at the HTTP_REFERRER header and for the q=string bit.
e.g. This is one of the adwords links in our adwords http://www.google.co.uk/aclk?sa=l&ai=CSh_Wsj58ULfSG6eQ0wX2lYGoCeeOl-oC58Cl-Drf1IC_TggAEAMguVQoA1CKi6VhYLu-roPQCqAB4feK9wPIAQGpApKunRBI7ro-qgQoT9ChS2VRrwOYoAh7INk0o-weepWecQHgrRXsbAAywxiTq8S-Q2z3EoAFkE4&sig=AOD64_13QvYMRHa0MIhPoLtM_hiFL9X-Mg&ved=0CC8Q0Qw&adurl=http://vzaar.com/landing/trial%3Fpartner%3Dadwords_Business-Video-UK&rct=j&q=online+video+hosting
You can see the the &q=.... parameter which comes across in the referrer header. If you extract that from the header you can work out what the search query keywords are.
(You can see it in the referral header here - http://i.stack.imgur.com/vLERe.jpg )
If the person has instant search on you wont get the keyword, the parameter q= shows up for static searches. In your Analytics go to Traffic Sources - Sources - Search - Organic you'll see in the keywords column
To track the keywords you can try adding keyword insertion into your target URL so when they click the Ad it'll be stored in Analytics as part of the landing pages URL
Similar to tagging your URL's only with this you'll add the keyword they searched to the URL so you have a record of it.
Here's two example searches one with instant search on one off
Instant Search on has no q= parameter at the end
Instant search off contains q=loan at the end