A really easy mistake to make when you’re building your campaign is to set up ad groups that have too many keywords in them.
An ad group is supposed to be a set of ads matched with a set of keywords. If you have too many keywords it’s just too hard to make all those keywords relevant to the ads that are in the ad group. The fewer keywords you can have the better, and sometimes you only want one keyword in an ad group because it’s an important keyword for you, that way you can write an ad specific to that keyword.
In general you’re going to want just a small set of keywords matched up with each ad.
You can avoid this mistake really by not following Google suggestions when you’re setting up your ad. They’re going to give you a long list of keywords – anything they think is somewhat relevant to your website. A lot of advertisers fall into the trap of adding all these keywords that Google suggests thinking that they have some relevance to your site, so when the person comes to your site they might be interested in what you have, and they might buy something from you. This is the wrong approach.
You want to focus on the most targeted most specific keywords that you have – keywords people type in when they are getting ready to buy. That’s how you’re going to ensure you have a profitable AdWords campaign.