It seems you can discover Long Tail Keywords using the Google Keyword Tool, or using Phrase and Broad Match keyword and examining the Matching Search Terms report. With Broad Match you can move the performing keywords into exact match, and the non-performing into negative match. (Typically it is best to use the precise broad match by putting the + sign in front of the keywords. Otherwise in my experience, the broad match is way too loose and you risk incurring very high costs with very low ROI.) It seems the major downside to this method is initially you are paying for clicks for non-performing keywords during the 'discovery' phase. Also you will need a minimum amount of click-thrus to determine if the keyword is performing. Unfortunately on many long tails, by definition of being a long tail, the traffic is low, so it could takes weeks, months, maybe even years to reach that minimum data point. So you may have to make some predictions based on looking at total numbers for groups of very similar keywords that matched. The other method is of course using the Keyword Tool. Using this method you reduce the amount of time and money you will have to waste discovering long tails initally. But you may miss some sales. You can use your intuition as to which long tails are most relevant and therefore have the highest probability of a positive ROI. The downside of this method is that it is time consuming (but only at first) to go through and evaluate and choose all the keywords, AND, more importantly, the Google Keyword tool will not show you all the possible long tails that may produce conversions for you. We have discovered this over and over seeing conversions on very very long tails that had we not had the broad match active, we would have never got the sale on that search because it was too low of volume to show up in the Keyword Tool. Example: You have a broad match: +brand +widget +sales And you get a match on the search: chicago brand widget sales but you don't have a store in Chicago (but you still want to advertise in that market for online sales so you can't use geographic targeting on the campaign to exclude this match). So then we would add chicago brand widget sales to the negative list. Unfortunately by that time, we already paid for at least one click. But the same broad keyword may have brought in a sale on the search "really cool looking brand widget sales" which only had a couple impressions and didn't show up on the Google Keyword Tool but only needed once click-thru to produce a sale (and a very large one at that!) I'm curious about the opinions of others on this subject. Thanks!