How to appoint an ad agency?

1. Who will service your account day-to-day : who will be assigned to your account and in what capacity should be established before you sign on the dotted line. You may work with amazing strategists but they wont be found on your account after-sale.
2. What does the agency know about your company? Act as if you are interviewing a job candidate to see if they've done their homework - do they know how your organization is structured, what you current marketing mix is, who is on your board of directors, what your brand voice is like, and how many visitors your website gets a month. The very best should be able to tell you things about your organization that even you don't know.
3. Consider the billing structure Will they pay-for-performance structure, a monthly invoicing system, or pay-up-front model? Ask for transparency into how you are charged and how the fees are determined. You don't want any hidden costs that come back and bite you later.
4. Gain insight into their internal culture ' : An agency partner is an extension of your internal department, so you want to make sure that its company culture meshes with yours. If you are a straight-laced corporate machine looking to partner with a laid back, young, and hip agency, the partnership may not work out. Ask if you would have beer with them outside of work and enjoy it? Such soft characteristics are important, because you will be spending a lot of time together.
5. Make them prove their value : Ask, "Why should we select you over another?" Look for intelligent answers beyond the buzzwords. Good businesses are introspective and can point out their flaws while also elaborating on the real value they bring. Do they have a particular proprietary technology that no other agency has? Do they offer a service that no other agency does? Look for candid answers about their strengths and weaknesses.
6. Are they up for a challenge?  True success doesn't come in the form of sugarcoated communication. It comes by challenging another's stance. Don't be afraid to onboard an agency that is willing to provide constructive recommendations for your company. You are hiring an agency to become better, more agile, and profitable, right? So ask the question, "Name a time when you've had to challenge a client, and how did you go about doing it." The answer to the second part of the question will help you gauge their level of respect and tact, as well.
7. Is the proof in the pudding? Does the potential content marketing agency have a killer blog and website copy? Does your creative agency have a beautiful but unfriendly website? When an agency talks the talk but doesn't walk the walk, it is a red flag. Take a few hours as a team to research the agency's online presence, past work, and any other company materials so you can gauge that it actually knows what it's doing.
8. Ask about analytics not trophies : In the '90s, awards, trophies, and accolades were the sign of an agency's true value; now, it's all "in the numbers." Client results are the true measure of success. Look for agencies that are able to prove past clients' success through metrics and can understand, analyze, and garner insight via pinpointed data. Ask the agency what exact metrics they use to gauge success. Is it mutually exclusive data, broken down by your in-house activity and results versus theirs? What types of listening and reporting tools do they use?
9. Ask for references agency websites sound the same: we're experienced … we'll deliver … we're creative … we put a premium on serving our clients." Get past the buzzwords by asking for two or three references from past clients. Ask questions similar to those you would the actual agency, and compare answers.