Mistake #1: Putting all of your keywords into one ad group-
Keyword relevance is of tantamount importance in any PPC campaign.
So, if you lump all of your keywords into one ad group, the impact will be some keywords become highly relevant to the ad group while others are not.
This is a common mistake marketers make thinking that the tactic will boost impressions. It will – but this approach is more expensive overall and those less relevant keywords that boost impressions are also likely less competitive and therefore less expensive when used in ads by themselves.
Mistake #2: Not testing ads-
Another common mistake marketers make is not testing their ads.
Unless you test, you’ll never discover what really works. Set up simple A/B tests and don't test more than one or two variables within an ad at a time. If you have an ad as a control and change 5 things within the ad you are still left speculating which of the five changes effected the performance. You want to test 5 changes set up five tests as there is no other way to effectively benchmark an ad’s performance efficiently.
Mistake #3: Sending all your traffic to the homepage-
Now where should you send your ad traffic?
Often marketers will send their ad traffic directly to the homepage, and this is a mistake.
The user found your ad based on their search criteria, Google matched the relevancy of your ad to that criteria and you want to send them to your home page to start all over. The best place to send them is either to a landing page designed specifically for relevance based on their search or to a relevant content page. If you can't provide the information a top of funnel user is looking for all your PPC campaigns will achieve is a higher bounce rate.