Here are the most common AdWords marketing mistakes:
Insufficient keyword research. You should begin with brainstorming, search through any available brochures, catalogs, and other marketing material related to your offer. Then use the Google Keyword tool, including other popular tools such as WordStream or Wordtracker.
Not knowing your conversion rate. If you don’t know the conversion rate of the product or service you are selling, then start slow with low daily budget.
Not writing effective ads or customizing them for your keywords.
Ineffective testing or not testing at all.
Irrelevant keywords to your ads.
Irrelevant ads to landing pages.
Not designating a spending limit for your campaigns.
Failing to track and analyze results.
Failing to optimize keyword, ads, and landing pages.
Quitting too soon, or not knowing when to quit. If you are not converting enough to make a profit, then make changes and monitor the results.
If you’re going to play the game, then you need to take your time to learn everything you possibly can about PPC advertising.