Tracking Your ROI (Return on investment)
This is one crucial stat you will need to know. You need to find out what keyword converts and what does not and sufficient knowledge in this stat will dramatically slash your advertising costs. Now Google offers Analytics which you can link to your adwords account and track your ad performance.

How to Improve ROI?
Improve conversion rates. This can be achieved by, improving quality of traffic, improving ad copy and improving the landing page.

Traffic Quality – Perhaps you are being on too general a term. You should be focused and specific and “drill down” on your keywords. Learn more on how to do that when you get a free copy of my “Secret Google Tactics”. Improving your traffic quality means getting viewers that are more targeted and, as a result, more warm to your pre-selling or product.

Ad Copy – Constant do split testing within each ad group. Test the same ad body with different headlines. Remember to set the ad showing to equal rotations instead of it showing only the ad with a higher click through. This is a continual renewal process which will force you to write better copies every time.

Landing page – Do you have your own landing page? If you are merely directing traffic to a affiliate link there is pretty much nothing you can do here but only to work on traffic quality and ad copy. If you do have your landing page, do constantly track and test the response rate. Try to capture or pre-sell your prospects. You can do this by having an email capture pop-up which is like an auto responder. Offer them something free (free courses, free book, etc…) in exchange for their information. This way, you still have a way of contacting your traffic.