So along the process of educating, comparing and buying a good or service it also makes sense then, to tailor your ads to each point along that graph too. I would even argue in many cases that you don't want to be found along the 1st two points of the graph, but nevertheless, let the data speak for itself-- i.e. track everything.
To put this into practice it makes most sense to have ad groups within a given campaign differentiated by keyword specificity as it relates to the buying process. Therefore it is a clear path to writing for the different targets. Ad group 1 is written for the uneducated searcher, ad group 2 to the price comparer and 3 (if different than step 2) is for the buyer with credit card in hand. Again, the keywords are making the distinctions for all 3 steps.
Confused about how this relates to your web site or online marketing? Let us know and we'll make it make sense customized to your business needs.