The outsourcing of project work is more common today than ever. But even though you outsource the work, you can't completely outsource your obligation to make sure the project is progressing smoothly. If all goes well with the outsourcer, you don't have much work to do. But many times the outsourcer doesn't perform to your expectations. If that happens, you want to know about it as soon as possible.
On a normal internal project, the project manager is held accountable for the success of the project, while other people monitor the work. On an outsourced project, the roles are still in place, but the vendor project manager is the one who's worried about the details of managing the work. The client project manager (you) takes on the role of monitoring the work and the progress. You need to ask the right questions to make sure the vendor is doing his job correctly. You don't necessarily need to know all the details but you have to feel comfortable that the project is progressing as expected.
At the beginning of the project you need to look for the up-front deliverables that you expect all projects to have. For example, the vendor project manager should have a Project Charter or Statement of Work document that describes what his team is doing. You need to make sure that the project is defined correctly and to your satisfaction, and that the vendor project manager has an adequate schedule. You should also approve his or her project manager procedures.
As the project is progressing, you must continue to ask questions to determine the current state of the work. You should have status meetings weekly and you should have a formal quality assurance check at the end of every agreed-upon milestone. You and your sponsor should formally approve the important deliverables. If there is a partial payment being made at a milestone, you need to ensure that the criteria for payment are all defined and that they are, in fact, completed.
Many people think that by outsourcing work, they're ridding themselves of the responsibility. That's only partially correct. Your organization must also monitor the work to ensure that the work's progressing as expected. Remember that vendor problems eventually become client problems.