I got a few blogs, using the same design, the CTR is very low, it never was above 1%. But I like this theme too much and looks professional. So I heard the best place to have the ads are within the post, on the left side, so I can put a 300x250 in a <div style="float:left;">. However, my posts have also images and YouTube embed codes. If there is an image for example near the start of the post, it will pass the usual space and go "outside" the layout. Any suggestion about this?
Depends on how you are monetizing the site. If your main method of monetization is affiliate stuff you don't want adsense above the fold and getting most of the attention. If adsense is the primary revenue earner I find just below the blog post title works well and below the post.