I am really curious to see how people answer this question. I do not believe there will be one clear cut answer because it seems like adsense taylors itself to what you write and who is viewing your article.
What is key to almost everything on the internet is wording. Vary your wording and find phrases that are searchable. I am a big fan of using Google Adword and a thesaurus.
If revenue is your goal, Amazon Affiliate Program and e-bay are great sources. I like to chose specific products on amazon that fit my article when possible and have E-bay as my random shuffle.