Like many things, designing solutions is a step-by-step process that not only involves: technical aspects, nor necessarily technical parties. Usually, you will be engaged by an account manager, project manager, or, if you are lucky, a CTO, who understands the technical part of the requirements. They are looking for an expert who can help them deliver a solution to a customer. These requests usually do not contain all the information you will need to deliver your solution, but it's a start to understand what your goal is.
For example, imagine that you receive an email from a project manager with the following statement.
We require a solution that can sustain at least 10,000 website hits and will stay available during updates as well as survive outages. Our budget is considerably low, so we need to spend as little as...