To increase CTR you need to try following things and I've done so far is:

You need to look at the quality of your content as well - If your content is not engaging, and if the visitor isn't reading anything off your content, and then just leaves your site, then most probably they will not click on anything at all on your site in the process. If you have quality content, and if the visitor reads more than 10 seconds of the content, then that will contribute to higher chances in clicking your ads.