I recently spoke with Jolien Demeyer, founder of Jelloow, an agency that connects startups with advertising and marketing agencies. Jelloow has about 3,000 agencies in their network, such as Deksia, with 40% in the US, 45% in Europe, and the remaining around the world. Most client companies are pre-seed through Series A, with about 20% later stage or large companies. She has seen it all and wants to help you win.

What are some classic mistakes you see when companies start advertising?

First, I find that many companies start with the wrong mindset. They’re skeptical about paying for advertising and don’t want to invest too much, then expect results too quickly and pull back when immediate results aren’t there. Part of the problem of rushing at the beginning is that companies do the work out of order. They spend $30k on graphics, Facebook, and LinkedIn but they never spend the time first to really figure out their messaging.

Second, I often talk to companies, and they say I’m focusing globally. You can’t focus on the whole world at the same time! It’s a sign that a company needs to prioritize.

The biggest problem of agencies is they usually say they do everything. If you have 10 employees, you can’t be great in every channel. But they want to get the business, so they say whatever they think the client wants to hear. When they overpromise and underdeliver, no one is happy.

Should a company prepare an advertising brief before picking an agency?

A company often doesn’t know what they need—and to some degree they shouldn’t. It’s like going to the doctor, you don’t go and say, I have liver problems. You go because you want to climb Mt. Everest, and the doctor will ask questions and then diagnose any potential issues. So I always try to discover the real need behind what a company tells me, and we suggest partners on the basis of that. I encourage founders to think through the need behind the need. Instead of “I need SEO” the real need might be “I want more organic customer leads.” The difference is important because it will give the agency more flexibility in delivering on the key metric the company really wants.

The other thing to think through is your customer journey. That defines your conversion funnel. And it usually requires content that you need to have in place to make the most of any advertising you do. Advertising just brings customers to your door. You need to make sure you give them what they need so your conversion is good.

What are the signs that an agency is a good fit for a startup, or not?

When you’re starting a relationship, you don’t just put yourself naked on the table. It’s Important for the brand to give its core message to the agency, but that takes time, particularly because the company may need help defining it. The agency has to do their homework, and challenge the brand. All of this takes time and is as much relationship development as it is business. Transparency is crucial. If you feel the brand or agency is holding back it won’t work. You need to schedule regular calls. KPIs must be set up and tracked.

Picking a good agency is not like buying bread. It’s a long process and both sides need to be a good match. That’s why we select five agencies that we think might be perfect for the company, but the company needs to talk with each one and see which feels best. And don’t forget—changing agencies is not hard.

If you could give startups one piece of advice, what would it be?

Be as clear as you can about what do you do, what you stand for, and which market you’re trying to reach. Really try to nail that down. If you can’t explain what you do in two sentences, then it will be hard to succeed with paid marketing. Consider using a messaging consultant first. Once you have growing revenue it’s good to have an agency. As you figure out what works, start bringing the most successful pieces in-house.