One of the most common reasons agency engagements start badly is that the startup and the agency both underestimate how much groundwork the startup needs to do before the agency can do anything useful.
The agency cannot build a strategy in a vacuum. They need real inputs from you, not polished ones, just honest ones.
The basics that must exist before anything else
Before a growth agency can begin working meaningfully, a few things need to be in place. The product needs to be stable enough that the customer experience is not broken. You need some form of analytics set up so that you can measure what is happening. And someone on your side needs to be available and empowered to make decisions quickly, because a lot of early growth work moves fast.
If any of those three are missing, the first weeks of an agency engagement will be spent fixing foundations rather than finding growth.
The information a good agency will ask for
A serious agency will want to understand your growth history before they suggest anything. That means: what channels have you tried, what results did you see, and what happened when you stopped or scaled them. Even if your data is patchy, sharing what exists helps the agency avoid repeating experiments you have already run.
They will also want to know your current customer acquisition cost and lifetime value, even if those numbers are rough. CAC and LTV are the foundation of almost every strategic decision in growth marketing. If you do not know them, figuring that out becomes the first task.
What you will be asked about your customers
Good agencies do their own customer research. But they also need your existing knowledge. Who is your best customer, not your average customer, your best one? What made them convert? What do they get out of your product that keeps them using it? Do you have any customer interviews, NPS responses, or support conversations that reveal how people actually talk about what you do?
This kind of qualitative information is often more useful than a full analytics report, particularly at early stages when sample sizes are small.
The strategic brief
Finally, you need to be able to tell the agency what success looks like and give them a realistic timeline to achieve it. That does not mean a detailed brief with fifty requirements. It means clarity on your North Star metric, the one number that genuinely reflects growth for your business, the budget available, and any constraints on channels, markets, or messaging.
If you cannot articulate what you are trying to achieve and why, an agency will either guess, which wastes time, or spend the first engagement working it out with you, which can feel slow but is often the most valuable work of all.
Come with your real numbers, your honest assessment of what has worked and what has not, and a named person who can make decisions. That is more valuable than a polished brief.