Bad quality scores on adwords

Hi all,

Looking for some PPC advice. Some of my adwords keywords have great quality scores, and some are awful.

I've looked at the awful ones and I've got ads that include that keyword. Apart from the fact that the keyword itself might not neccesarily be present on the landing page (although very close alternatives to that keyword are on there), what can I do to improve my quality score? Is it just a case of trying out different ads that perform better and improve my CTR?

Thanks