Hire the studio that can show you a brand still standing up two years after it launched, not the one with the best-looking portfolio. Those are often different studios. A portfolio shows launch day, photographed kindly and cropped to flatter. What you are buying is everything after that, when the brand is being used by people who were never in the room, on things nobody made a mockup of.
You do not need a designer's eye to read a portfolio, you need three questions. Does the work change from client to client, or is every project wearing the same house style with a different name on it. Does it go past the logo into the things a business actually runs on, a website, packaging, an app, a deck, signage. And can you tell what each business was trying to say that its competitors were not. If the case studies are all a mark on a grey background and a tote bag, you are looking at a design exercise. A brand that has been through a real company has scuffs on it, and the studios who have done that work tend to show the awkward parts too.
The first call tells you more than the deck. Ask what the client had before, what changed for the business afterwards, and what the studio would do differently now. Anyone with real projects behind them will talk about the parts that went sideways, because every project has them. A studio with nothing but triumphs is either managing you or has not shipped much. Ask who does the work, as well. In a small studio the person on the call is the person who draws. In larger ones the pitch team and the delivery team are different people, and it is fair to ask which of them you are hiring.
Watch whether they ask you anything before quoting. A studio that can price a brand off a one-line email is pricing a logo, and you find that out later, when you ask for the rest of it. Proper scoping asks what you sell and to whom, who you are up against, everywhere the brand has to show up, and what it costs the business if it lands wrong. That conversation is also the best sample you will get of what working together feels like. Being asked good, slightly uncomfortable questions is the sign you want.
Some things should end the conversation. Packages sold by the number of logo concepts, because thirty options is a volume business and a good mark comes from narrowing down, not from a menu. Design contests, where dozens of strangers work for free and none of them ever asked you a question. A mood board presented as strategy. A portfolio where every project looks like whatever won awards last year, which tells you the taste is borrowed and will date on the same schedule. The subtler one is a studio that designs brands but has never built the website the brand has to live on. Identities made in a vacuum come apart the moment someone has to code them, and you end up paying a second team to quietly redraw the first team's work.
How many studios should you speak to. Fewer than you think. Three is plenty, and eight gets you a spreadsheet, a lost fortnight, and a decision made on price because everything else has blurred together. Choose the three whose past work sits closest to the job in front of you, brief them identically, and see who comes back with the better questions rather than the faster answer. Get the boring parts in writing before you sign, the deliverables, the number of revision rounds, the timeline, who owns what at the end. That is hygiene. The choice itself is made on the questions.
So write the brief before you write the emails. One page: what your business does, who you need to convince, everywhere the brand has to show up in the next year, and what it costs you if people keep misreading you. Send that same page to three studios. The one that comes back having noticed something about your business you never said out loud is the one to hire, and it is usually obvious inside the hour.