It's all about positioning!
To start off, take a look at your website and analyze, which part of your template you see in the first place. That is the place for your adsense. Usually it's better to add your Adsense links right in the middle of your theme or in the middle of your content maybe just above it.
What about the best performing ad units -
Leaderboards & Skyscrapers:
These ad units are the most converting for me. Placement of these are obvious, on the top of your page (just under the title) - for leaderboards and in your sidebar for skyscrapers.
These ad units usually get high CTR, because of good placement within the website template. Make sure to match the colors too.
Square & Rectangle Ad Units:
My second favorite ones. These get a lot of clicks, but if you have targeted readers. Your job is to make your content interesting, if you have that - users will be likely to click ads to expand their knowlegde on the selected niche.
Usually, I get the biggest rectangle and wrap it around my article (top left or top right). It's not worth putting them in the bottom of the page or article, because many people don't even get that far, especially if your content is not that useful for them.
These are the snikiest earners for you. You can disguise these as menu items, and usually users click those without noticing that they are clicking the ad. To get your win-win situation you have to pick the colors and sizes right, it's crucial for you.
Personally, once in a while I find myself clicking on a menu link unit without even thinking about it. After a short while I realize I've just made money to the website owner. I wonder how much tired people get caught on it, but hey, it's good for us, isn't it?
So, before you start placing ads on your website, think about your positioning. If you optimize your links right, you'd be getting 10% CTR easily.