We had tried outsourcing some of our software development overseas and found it very difficult given the time and language barriers. I would suggest the most important thing you can do is pilot a program. Make sure that the pilot starts with a very simple task with little or no learned skill. First it will be less expensive and you will be able to easily see if the communication/time zone is going to be an issue.

The other thing to consider is the quality of the firm. It is worth spending sometime upfront finding a quality firm like anywhere there are wide variations of service and you should find a firm that has outsourced in the past and has good referrals.