Step #1 - You have to make sure you can find at least a couple of competitors who are using the keywords you are trying to use.
The bottom line is that you have to make sure you are not the only one buying traffic from the search terms that you are looking at using.
If you can find one or two good marketers who are using the search terms you are bidding on, that usually means they are making a profit. This means that the traffic is buying stuff that is being sold and you are going to have a better chance at making a profit.
Step #2 - You have to make sure you are only starting with the keywords that match your product.
You have to make sure that when you start out with this source in your niche that you only focus on the search terms that match what you are selling. That way you can be sure you are using the right terms that will give you the most amount of profits.
Don't use the high search volume terms in your niche until you have proven to yourself that you can make a profit off the ones that match your products.
Test out these two strategies so you can start making more money from the search terms in your niche.