A campaign's audience is the people Meta will show your ad to, and you define it with a handful of criteria: age, area and interests. It is the decision that saves or wastes the most money, because an excellent ad shown to someone who does not care sells nothing.

Describe your customer before touching anything. The most common mistake when starting out is leaving the targeting very open for fear of losing sales. The opposite happens: the money gets spread among thousands of people who were never going to buy from you.

• Where they are. For a local business this matters most of all: your town or a radius of kilometres around your door. Being seen by someone three hundred kilometres away is of little use.
• What age they are and what interests them. Think about which other brands, magazines or accounts the people who already buy from you follow. That is more useful than guessing.
• How many people it is. An audience of a few thousand wears out in days, because those people get your ad constantly. One of several million dilutes the budget. To start with, a middling size clearly related to what you sell works better than the extremes.

The hours matter. You can advertise twenty-four hours a day, but your audience is not looking at their phone in all of them. Generally the midday and the late afternoon and evening slots hold the attention, and Monday to Thursday tends to sell better than the weekend. It is not a law: what counts is looking at your own data in Performance after a few weeks (see «Performance»).

When the audience wears out. If frequency, which is the average number of times each person has seen your ad, starts rising without stopping, you have two ways out: change the ad or widen the audience. BOOST, Markettai's automatic system, does the second in steps when it detects the problem: first it loosens the interests, then it widens the area and, as a last resort, it lets Meta search on its own (see «What the system does while you sleep»).