I came across this graph today and thought it was worthing passing along. This is well researched info on some easy ways to increase your PPC ad landing page conversion. Obviously these are general rules and you would really have to test your own results, but at least these give you a start on what to concentrate on.
Obviously the best results are obtained from repeated testing and tweaking your page, but it is interesting to see that removing navigation produces such a big effect. What they mean of coarse is removing standard site navigation so that the visitors only focus is the offer.