How to Decrease Google CPM

1. Lower the default CPM bid for the campaign. Every campaign has a maximum bid that may be changed at any time. Once inside the campaign editing screen, you can lower your bid to $0.25 CPM, the minimum allowed by Google. Use the 'Calculate Weekly Estimates' button on the same screen to see how many impressions your ad will generate at the new bid price. Increase the bid in stages until you reach an acceptable impression-to-cost ratio for your budget.
2. Regroup the keywords used to trigger your ads. Each keyword you choose is assigned a value. In certain cases, the values between individual keywords may be $20 per click or more. Reorganizing your keywords into groups based on their relative values will often result in a decrease of CPM. Free tools such as the Google Adword Keyword Tool can help establish the average value of each keyword to help you organize the groups properly.

3. Change the CPM bid for 'Automatic Placement' ads. These are the placements Google chooses for you based on your keywords and the bid amount you enter. Lowering the bid here changes the CPM of your campaign and allows you to maximize your return on investment (ROI) by finding a happy medium between your cost and click-through ratio on these types of ads.
4. Decrease the CPM bid on 'Managed Placements.' This is the other option Google offers for the display network. You manually ad specific sites within the network that have a high visitor volume and seem to be the most in line with your ad content. Each individual site has its own CPM bid, which may be raised or lowered according to the results your ad produces on the network. Lower the CPM bid on those sites with poor click-through rates to lower the overall CPM cost of your campaign.
5. Adjust the audience settings to decrease Google CPM. Adwords allows you to choose who sees your ads based on a number of demographic factors including age, sex and geographic location. Expanding or narrowing your targeting will change the overall CPM of your campaign. You must test each factor individually to see which way to adjust your settings for your particular campaign. For example, targeting women usually results in an increase in CPM; targeting men between the ages of 35 and 45 may lower the CPM for the same set of keywords.