1) Someone that you UNDERSTAND... and makes YOU feel UNDERSTOOD.
A designer must be able to interpret your vision, needs, wants, style, and budget (just to name a few) when planning your space. They need to communicate in language that you understand, and they need to be able to clarify when you don't. The designer must be able to explain all the steps required for your design, which trades are responsible for which aspects, what your role is, what the payment schedule will be, when to expect each phase of the process to move along, and so much more. Also, you want to connect with the designer and have fun through the process. Working along side someone incredibly dull likely won’t motivate you to want to get through the project.
2) Someone that is organized and manages all aspects of the project... so you don't feel like you have to babysit.
A designer's top priority is ensuring that you are up to date and understand each step of the renovation and design process, but they first must be able to determine what those steps are. Consultation, proper measurements and initial inspection, sourcing materials, creating a design plan, using their software and tools to create visuals, collaborating and communicating, budgeting, organizing and curating the supply list, buying the right amount, communicating with and scheduling the trades persons, knowing which trade is required at which step in the job, organizing invoices, meeting deadlines... there is a LOT to one project. You need someone who can keep on top of all the details while managing and coordinating with all the people or moving parts.
3) Someone that offers ideas that will PRACTICALLY and FUNCTIONALLY fit your lifestyle, while still looking fantastic.
Designing innovative interior spaces that meet the clients’ budget and requirements, both in terms of functionality and aesthetics is a designer's job. Offering ideas that redesign a space to be more practical and aligned with the intended use than the client can imagine themselves is one key function of a designer's value. You may be able to imagine the overall function and vague style of a space... but a designer gets right down to the small details that you may not have even dreamed of, like how much knee space is required for a bar-height chair vs a standard table height. Suggesting materials that align with the function and vision of the space ensures your project is built to endure it's intended function. A designer should keep up-to-date on the industry’s current trends and recent developments in terms of techniques and consistently be aware of products and materials available.
4) Someone who understands the building code compliance, so your roof doesn't fall down on you after your project is done.
Okay, so maybe your roof falling down is a bit of an exaggeration... but you don't want to finish a project only to have issues later and find out it wasn't done to code in the first place. A designer must ensure that plans are compliant with all applicable building regulations and safety codes. This is a key part of a designer's training. If they are assuming the role of a general contractor or project manager, they must be capable of ensuring all the trades people are complying with the local building code. If the designer is not educated on the building code standards, they must be working in tangent with a trades person that is. (Ensuring that the trades people completing the renovation work have their Red Seal accreditation is a great idea.) Promoting eco-friendly practices and materials and employing them whenever possible is something that many designers emphasize as an important quality this day in age.
5) Someone who can help you SEE their vision.
A designer can provide you with a plethora of tools in order to visualize your design plan. This can be hand drawn sketches, floor plans, 3D software, swatch books with different fabric choices, elaborate design boards with real samples of suggested materials, lookbooks... the list goes on. The bottom line is that you want to make sure you understand what the finished project is going to look like and how much it's going to cost, right down to the detail (mapping out the location of existing and envisioned walls, windows, doors, electrical outlets, and lighting fixtures, for example.) Find a designer that has the tools that YOU need to feel like you really understand the final product that you are getting.