Broken Toilet Scenario 1:
Your toilet backs up. You have two options. Call a plumber, or attempt to fix it yourself risking a possible disgusting disaster. You make the smart choice and call the plumber. While this costs money, you are smart and realize that the time and effort you are saving by hiring someone that is qualified to fix your problem is well worth it. True, you may have been able to fix it yourself, but you also may have made it much (much) worse.
Remember this scenario when choosing an ad agency, and use the same mindset. You run a successful business. You are a smart and capable businessman. You realize that your business could get more exposure so you do your research and hire an equally smart and capable ad agency to assist in promoting your business.
Once you hire said agency, and they prove to you that they actually do know what they are talking about, let them do their job. You hired them for a reason. Remember that. Yes, you are the client and you have every right to be informed and involved in the decision process, but also know that this is not your expertise and that your agency really does want the best for you.
Trust your agency. If you find yourself questioning their methods, ask questions as opposed to taking matters into your own hands. Any good agency will welcome your criticism and be more than happy to explain the reasoning behind their methods.
Broken Toilet Scenario 2:
So, you call the plumber. He shows up and fixes your toilet. Bright and shiny and new! You then decide that you can do a better job and you shove and armadillo in the tank. That should do it!
DO NOT DO THIS. By undertaking a task yourself that you may think is the right thing to do, you could do some serious damage. Loss of revenue, poor strategy changes, or at the very least, make more work for your agency to spend time fixing things, that they would have been spending making you more money. Always ask questions. Chances are, there are very good reasons that they are doing what they are doing, you just may not understand. Knowledge is power. And power is for rangers.