Measuring the success of an ad depends on the goal that you have set for your ad. Different goals require different metrics to evaluate the performance of your ad. Here are some common goals and metrics that you can use to measure the success of an ad:

• Brand awareness: This goal is to increase the recognition and recall of your brand among your target audience. Some metrics that you can use to measure brand awareness are impressions, reach, frequency, and brand lift. Impressions are the number of times your ad is shown to your audience. Reach is the number of unique people who see your ad. Frequency is the average number of times your ad is shown to each person. Brand lift is the increase in brand awareness, preference, or intent among your audience after seeing your ad.
• Lead generation: This goal is to collect information from potential customers who are interested in your product or service. Some metrics that you can use to measure lead generation are clicks, conversions, cost per lead, and lead quality. Clicks are the number of times your audience clicks on your ad or call to action. Conversions are the number of times your audience completes a desired action on your landing page, such as filling out a form or downloading a file. Cost per lead is the amount of money you spend on your ad divided by the number of leads you generate. Lead quality is the relevance and value of the leads you generate for your business.
• Sales: This goal is to increase the revenue or profit from your product or service. Some metrics that you can use to measure sales are sales volume, sales value, return on ad spend, and customer lifetime value. Sales volume is the number of units or items that you sell as a result of your ad. Sales value is the amount of money that you earn from the sales that you make as a result of your ad. Return on ad spend is the ratio of revenue to cost from your ad campaign. Customer lifetime value is the estimated net profit that you can expect from a customer over their entire relationship with your business.

These are some of the many ways that you can measure the success of an ad based on your brand's goals.

There are many other factors that can affect the success of an ad such as the quality, creativity, timing, and placement of your ad. You also need to consider the context and behavior of your audience and how they respond to your ad. 

You can also use tools such as Google Analytics, Facebook Ad Manager, or HubSpot to collect and analyze data about your ads and optimize them for better results.

You can also use that data to inform the design of surveys and focus groups to help refine the campaign effectiveness off and on line.

The most important lessons I learned from my time working with American Express and Oglivy & Mather Advertising. 

• Employ a marketing team that believes in ongoing ad variation testing - and retesting - over time. 10-20-30 years. Not a few weeks.
• Use many different (online and offline) tools to help you define your brand's [dynamic] marketing terrain and your brand's position on it.
• Explore corroborating research findings as well as the anomalies. The latter will teach you more than the former. 
• Remain humble and curious.  
• If you're not having fun - move on and hand the brand building role to those that are.

Banksy

I just saw this online - with no credits, and it reminded me of my father who was a Master Cabinet Maker in Germany before he and our family moved to Canada after WW2. He used to tell me stories about some of the clients that came to the family business in the early 1900s with their unrealistic design, delivery date and price expectations.

In Canada he managed the construction and subsequent maintenance of a dozen large office buildings in Toronto. He used to tell me stories about some of the clients that came to the construction company's head office with their unrealistic design, delivery date and price expectations.

While I spent my career in advertising, I ran into my share of those clients too. They didn't know much, but they all knew how to make any well thought out idea or campaign much "better", how to get the job to the finish line faster, and how do do it cheaper.

Clearly this studio has met one too many clients who know it all.

I love their polite response.