If CTR is low, then people don't click on your ads often enough. Write attractive ads, which will bring you more clicks. Your keywords+ads+landing have to be tightly connected.
you can get a high QS even if your CTR is low to start off with make sure your site is relevant to your keywords. it would be great if your keyword can be in the headline of your landing page, or in the title add the keywords you are bidding under to your meta keywords too
I wrote a page about improving your advert's CTR in my guide: http://www.epiphanysolutions.co.uk/...advert-text/maximising-the-click-through-rate I'd suggest doing a Google search for your advert (use www.google.com/adpreview), and try to figure out why people are clicking on somebody else's advert instead of yours. Do they catch the eye? Are they quoting prices? Are they more targeted to what the searcher was looking for?
make sure your site has all the necessary components: Privacy Policy, Contact Us, Easy Navigation META Keywords, Title, Description And Relevancy to the keyword you use in your site text.