Start with SpyFu Kombat: entering your competitors’ domains along with your own will give you their shared keywords that you don’t already buy.
Details: Start with Kombat
1. Enter your own domain into the SpyFu search box. Choose “PPC Research > Kombat” from the menu options.
As long as you have an AdWords campaign underway (and we see you appearing on keywords) we can find your competitors automatically.*
* You can override the competitors we found and compare other domains instead. Follow Step 1 and wait for the page to load with two extra domain fields. Just keep your domain in the first box and search again.
2. Scroll down to the results. You will see circles that represent the keywords that each domain (you + 2 biggest competitors) buys.
3. Look at the titles on the right. Choose the “Buy Recommendations” segment. It’s the set of keywords that appear in both of your competitors’ list of paid keywords — leaving out any of your keywords. These are terms they share that you don’t buy already.
4. The actual keywords open in a list below. These are keywords that BOTH of your listed competitors have bet on by purchasing them in AdWords. We believe that while either competitor might dabble in a few unprofitable keywords, both competitors are going to agree on the ones that pay off in the long run. Since you excluded your own domain’s keywords (by choosing the Buy Recommendations (overlap of competitors without your domain), this list is filtered to competitors’ best keywords you should buy, too.
5. You can sort them or select specific keywords before exporting them (using the button at the top of the chart).