Before you ever speak to a designer, take some time to think about what you want, what you need, what you can afford, and what is most important to you. The designer you hire will be able to advise you on specifics, but to get the result you want, it is important to do your homework first. The time you spend will be well worth it.
Once you have determined the scope of your project, spend some time considering the "look" and options you want. Putting together a Pinterest board of your likes and dislikes, wishes and dreams is a great way to begin the design process. Look for pictures of rooms or styles that appeal to you, swatches of fabric, paint color cards, furniture catalogs or brochures, etc. These will stir your imagination and help the designer better understand your preferences and tastes. Include information and pictures of appliances, plumbing fixtures, lighting fixtures, cabinet and door hardware, and flooring materials as well, if these will be elements in your project.
Finally, consider how much you want to be involved in your project? Do you want a designer who will work with you, or do you want the designer to take charge and provide you with options? Clarifying your expectations will help you and the designer to communicate well and ensure the result you want.
When you hire an interior designer, you get the benefit of an experienced professional who can solve problems, help you avoid costly mistakes and, most importantly, create a space designed specifically to meet your needs.