Another piece of selecting an agency is to play an active role in the partners (other agencies) that they work with and recommend you select. There are two scenarios here.

First: there are times when large agencies will have select partners they recommend, allowing them more involvement with your business even if they don’t have the expertise in-house. For example, if a large advertising agency doesn’t have expertise in interactive, they (hopefully) will recommend a partner they prefer. On one hand, this may benefit you since they have experience working together, but in the end it is important that you play a part in managing that partner and their role in your account. It’s also important that you do your own homework, checking out several agencies before making a decision if it is a significant element of your overall marketing program.

Second: an agency that will not have the expertise in-house to handle all of your needs will hide partners and claim the work as their own. Make sure you are well aware of the internal resources and in-house capabilities before you sign on, or you may be wasting a lot of time and money. Smarter agencies will bring proven partners to the table from the beginning, rather than hiding the fact that they plan to outsource the project to a firm better qualified and prepared to handle it.

What you should look for is communication flow and one point of contact. Who will be responsible if a deliverable isn’t met?

Some specific tips to consider:

1. Draft a legal contract that spells out exactly what each agency will do, who is the main point of contact, how billing will be handled, who is responsible for deliverables, et cetera. "XYZ agency responsibilities will start here and end here." Keep in mind that there may be overlapping capabilities among your agencies, with the exception of totally vertical agencies that specialize in email or SEM. Your work may shift to another one of your agencies who has more bandwidth as your campaign moves forward.
2. Consider establishing a bonus structure for the group of agencies based on communication, performance and the overall success of the campaign—not just the individual pieces. Many agencies are sticking their necks out to prove they are worthy of the risk involved on a new idea or marketing channel.