Well depends on what you want the visitors to do. But a few points that worked for me in the past.
1) TRUST - client testimonials, or brand icons should be above the fold
2) Your Promise + Customer Hot line - again related to trust but more over something for the people to ring and you can convert over the phone (if applicable to your business)
3) Be Honest. Depending on how small or large your business/product/product group is you can try with - you are here because you clicked on Adwords . For this reason we offer x,y,z to YOU as a bonus. You will be surprised how many people might like the straight arrow approach.
4) Again depending on service/product/niche you are in - customer journey can be the single most important factor. If you sell high quality, but pricier sinks for example, dont go with BEST PRICES SINKS as you you leave the wrong impression. Instead try Best Value Sinks or Best Value Luxury Sinks. - YES your initial CTR might fall but in the end if you convert more - should I say more?
Those are just 101 things regarding customer behaviour, if you need more in depth analysis you can consult a PPC team (go for marketing studio and not the big agencies - pro tip from experience :) )
<snip>
[edited by: buckworks at 5:55 pm (utc) on Oct 29, 2014]
[edit reason] No solicitations, please. [/edit]