To succeed in affiliate marketing, you need to understand the Keyword Effectiveness Index (KEI). My favorite online tool for finding keywords and gauging their popularity online is www.WordTracker.com

They have a free trial you can tinker with. It works OK but it’s fairly limited. To get the advanced features, of course, you’ll have to buy a 1-day or 1-week subscription.

This, of course, ties in with what I’ve told you about marketing.
Once you’re in WordTracker, decide whether you need to use the “keyword universe” or the “full search” option. The “keyword universe” option is best for niche phrases, while “full search” gives a broader range of keywords. Here’s a quick guide to using WordTracker.

Notes:
• WordTracker isn’t perfect. It’s been known to assign high KEI to words with low Count (bad) and very low (or zero) Competing (good). Don’t target these keywords. Just go for the ones with high Count (not less than 100) and then look at Competing.

• One thing to know about the free trial is that it only uses MSN to determine the amount of your competition. What you’ll want to do is check the competitiveness of your best keywords on Google. Search for each by using an exact match search (i.e. you should wrap the search phrase in quotes, for example, “finding keywords”) and write down the number of sites that Google brings back. These numbers are usually much higher than MSN’s, and KEIs are thus lower.

Here are some other good sources for sourcing and refining your keyword selection. After sourcing your original group of keywords it is important to keep an eye on the successful keywords as well as the keywords that are costing rather than making money.

1. Use the Google suggestion tool.
Check out https://adwords.google.com/select/keywordsandbox.Run your keywords through that tool, and don’t just look up specific keywords (which is also a good way to find keywords to add), but also peruse the expanded broadmatch since keywords may show for these terms. And if you see more keywords that aren’t related to your product, add a few more. Keep on adding negative keywords with your words in the suggestion tool until everything that you see, period, is related to what you’re selling.

2. Site Logs.
Take the time to analyze your site logs (or interface program) to determine the keywords people are searching for that do not relate to your page. Every time
you see a query that brought somebody to your site and you don’t want to pay for that click, add that to your negative keyword list.

3. Do Your Ad Exercises
As long as you have the SERPs open, check out the other ads. Do you see ads which are unrelated? Often these ads are similar to yours since you’re doing keyword research for your own products. If you see ads listed that don’t fit, think about why they’re showing, and what you’d add to make these ads not show for this keyword. Also, think about what keywords are more likely to make a good CTR/ROI. Ongoing exercises like this can help you think of more keywords.

4. Overture inventory tool:
http://inventory.overture.com/d/searchinventory/suggestion/
Type in keywords and look for queries for which you don’t want to be shown. If they come up, then add more negative keywords. I recommend you use slightly more general queries than your actual keywords if you start to see some really small volume numbers just to get a bigger picture of the keyword combinations that can actually occur with your specific keywords.

However, you should always start with the most obvious negatives and have your conversion tracking system in place—otherwise you’re shooting in the dark. Make sure you don’t dial your exposure down too much—you CAN be too narrow, too selective. There are many profitable keywords that seem like they should be negatived out, but if they provide some ROI, then maybe you ought to keep them as comparison keywords instead.

If you start adding lots of negatives and you see your CTR go up, but your total conversions take a dive, then you probably went too far and need to dial it back on negatives. Google gives you a lot of control on exactly what queries bring up your keywords. Use the tools to make sure your keywords get the most profitable exposure possible.