This Adsense ad unit in top left or right corner have highest CTR on most of the blogs. Adding this ad unit is very simple and requires a bit of code before and after your regular Adsense ad script.
If you want to add a ad unit in top right corner of your post, then just include the following bolded red lines in your ad code:
<div style="float:right;">Your Adsense ad script
</div>
If you want to place ad unit at left corner, just change the float tag to "left":
<div style="float:left;">
Your Adsense ad script
</div>
The most appropriate for this ad placement is 250×250 square ad unit. Placing AdSense unit in the middle of the post, may disturb the reading flow, so i recommend to have ad units at the beginning of the post.
If you have any query adding this ad unit in your blog post, just leave a comment.