Thats a good trick, to sort out who doesnt pay attention to detail. I`d like personally weight in on, testing the persons skill, and test them out before anything. And even after that, agree on more outsource work them after "my sets of qualifications".
It really depends on what type of services you are willing to give. There are some services that works best on specifics sites. So far, I have only used SEOClerks until now, and I'm happy on what I'm experiencing as a buyer and a service provider.
For me, its seoclerks and fiverr. I have earned money from both sites. elance is also a good freelancing site but getting a project takes ages.
I prefer buying services on Seoclerks. Fiverr has one huge rival and that's seoclerks in my honest opinion. You can grab some amazing services for a dirt-cheap price of $1.00.. Not even Fiverr has that.
There are some with good feedbacks from buyers. Of course, the decision on buying that gig still remains on the buyer.
There is odesk.com and elance.com along with many others but if you are just starting up, you'll have some issues building an adequate client following. I am not using these myself but have experience using both of them in the past.
I personally like Elance and freelancer. I have used both extensively and as long as you know how to vet the candidates you will find gems at either place.