Don't believe what they tell you about Adsense placement!
Having had the site running for a few weeks and having actively monitored the Adsense statistics I started reading up on advert placement and general Adsense strategies to get and idea on ways to improve my click-through rate and, ultimately, revenue.
For example, the Google Adsense documentation recommends placing adverts at the top, top-left or just above the main content in the centre for the best results.
However, having spent a week tweeking the site and trying out all the techniques and seeing my revenues plummet it turns out that the most effective position is the bottom right of the screen - exactly where I had them (by pure chance) and contrary to what both Google and many other 'experts' say.
This highlights the importance of context to site design, search engine optimisation and advert placement strategies. Don't blindly trust what people are telling you, but use a planned cycle of modify-monitor-measure to determine what is best for you.