A big mistake that I see in a lot of advertisers accounts are keywords that are very loosely related to what’s actually being sold.
It’s really easy to do because when you’re setting up an account and building your campaign, Google suggests a lot of keywords for you based on the content of your site. The problem with this is these suggestions are not specific. They are very broad.
So if you go ahead and add all these keywords that Google wants you to you end up with a mess in your account and you will bring in traffic from people who don’t really have an interest in buying what you offer. They may be searching for something that is just kind of loosely related to whatever it is you sell, they see your ad, and now the end up on your site. They realize it wasn’t what they were looking for and they leave right away. Meanwhile, you have just paid for them to come to your site. Huge waste of money.
So when you’re going through and adding keywords to your campaign, make sure they are as targeted and relevant as possible.