Your target audience is everyone who is browsing internet or at-least the majority of them. Your objective can be any of the objectives listed above. The main players are Classified Sites, Travel, Dating Sites, Portals, Auto Sites, and other websites which attract amount of traffic:

i) The best Ad position is #3 with conspicuous ad text

ii) 20% of the keywords generate 80% of the relevant traffic.

iii) The long tail of keywords helps in maintaining the average cost per acquisition for entire program.

iv) There is always a list of negative keywords, negative sites where you don?t want to display. Unless you don?t care about branding.

v) Small changes might make great impact.

a. Test and try Different Ads to maximize CTR

b. Land Users on relevant pages