How to recognize a good traffic exchange?
Look for services where the exchange is based on credits only, avoid those where one gets pennies or cents to view your ads. Too many people do just try to collect the cash rewards and do not pay any attention to what they see.
It's also quite obvious that this cashrewards do attract cheaters, and those won't buy anything from you at all.
Secondly watch out for those TE's which offer a fair ratio for your views. Some do only give 0.3 views in reeturn for one of your clicks. Even if you are a free member only you should expect at least 0.5 views in return for your effort of clicking. Otherwise I call it click slavery :)
Also be aware that some TE's offer members to view ads in less than 8 seconds, which is hillarious some ads do not even open in that time.
That narrows it already pretty much down, but if you think that every upgrade is worth the money even though all the above is optimized then you also may pay attention to how much credits one gets monthly for an upgrade.
Some Te's give so many monthly credits that paid customers never ever need to click on anything. Well wouldn't you prefer that your ads are seen buy people who do not just hunt for FREE goodies?
The best traffic exchanges are well balanced and try to keep their member database free from cheaters, such who use bots just to have free exposure.
At WEM you find a list of traffic exchanges which have proven to care about their members. I even created a splash which makes that list available to promote all those at one time.
You may have a short look at it.
Since i have the profit tracker installed at WEM, I can see clearly which TE's are delivering not just traffic but signups and sales as well.