You must analyze the numbers in your tracking for the solo ad after every run. This is what tells you if you have found good vendor traffic.
1. Make sure that you received all the clicks your purchased. You will often have more, but at least make sure you are not short changed.
2. Check the optin rate. How many people of the number of clicks ordered actually opted in? If this number is less than your normal optin rate, this is a red flag. You might not want to use this vendor again.
3. Check the number of sales. If you getting the optin on your own landing page, but then sending them to an affiliate offer you don't control, this is more difficult to determine. What I do in that case, is create a funnel for each vendor I'm running the ad with and when I receive a notification of a purchase from the affiliate offer, I go see which landing page that person used to optin. This gives me the details I need to track any sales a solo ad vendor traffic generated.
NOTE: If there are zero sales for a solo ad vendor, that is another red flag.
4. Check the traffic quality. If the vendor said they would send 80% tier 1 or higher, make sure that is what you got. Using Clickmagick that is easy to do, I'm not sure with other tracking tools how you would do this. If the Tier 1 traffic is lower than you were told, this is another red flag.
NOTE: there is a button above in this post that gives you a 14 day free trial of Clickmagick if you don't already have it.
So the way to proceed from here is to see if there is one or more red flags for this solo ad vendor. If there is more than one, just don't use them again. If there is only one, then you might send another test run through them to see if this was just an anomaly.
Either way, if there was a problem with the traffic for any reason, let the vendor know. They will often work with you to try to make you whole on it.
If there are no red flags for a solo ad vendor, increase the next order with them. I would wait a couple of weeks to make sure they have time to add new people to their list. Then give them the order for more clicks. Then make sure and check results again. If it stays consistent after increasing, you may be onto a really good traffic source.
This post has been over a lot of ground. If you follow it, you will be able to start putting together your strategy for placing solo ads. My recommendation to you is to set your strategy and stick with it consistently for every vendor and solo ad placed.
Let me know any questions. I tried to make this simple to follow but may have introduced some confusion. If so, I would love to hear where you are having any issues so that I could clarify and assist you in your journey.
I'd also love to hear any good results you have. That would just make my day!
To your success!