It's all about trial and error, trying different structures, keywords and web site templates in order to increase ROI and conversion.
Different ad positions, some attract higher CTR and it's not always the first ones.. there are several techniques you can use such as placing your ad next to a competitors ad and offering a price which is slightly lower and more attractive.
Keep an eye on what you spend and where you spend it, with good analysis I'm sure you can have a succesful campaign.
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