First, prep for inflated bids as newcomers jump into the market and blind bid on broad terms for top placement from the onset. Smeland says to invest more heavily in less expensive, more specific keywords that may garner less traffic--but higher conversions.
Pay attention to your ads' Quality Scores by maintaining landing page relevance and high CTRs. In addition, experiment with the various targeting options available (such as geo- and demographic) to improve clicks and conversions. Meanwhile, think about reaching consumers through cost-effective, targeted offline options like airline magazines--or even testing Yahoo and Google's TV and radio products.