PPM Quick Tips : Outsourcing
Be as cynical as you can with suppliers. It keeps them on their toes; they will work harder to satisfy you, and it should stop you from becoming complacent.
Never believe any delivery deadlines until they are met.
Never assume that deliverables can be relied upon until validated by your people.
Assume the worse and build plenty of contingency into your project and programme plans.
Above all make sure the vendor is stable. Suppliers need to be financially sound, profitable and has a good track record of delivery.