Don't take their word that they can do something. Never hire without proof of their skills and examples of their work.

Also, communication is a big factor in hiring a freelancer. If you are outsourcing something to someone in another part of the world, watch out for timezone differences as well as making sure the person is a good communicator.

It's also just good general advice to always have them invoice you, just so you can have it on record for tax purposes.