You must have a detailed plan. This would consist of detailed drawings and a list of all materials and how they are being used. If you are planning an addition or a complete rethink of your home beyond the walls of the existing kitchen you may first need to hire an architect to start to explore structural, zoning and general utilization questions.
For detailed planning of the kitchen space per se your best option is to find a Kitchen Designer with many years experience at a studio whose portfolio demonstrates a style, quality and level of detail you find appealing. In most instances you can have several meetings to interview and qualify any of these people for compatibility, creativity, and skill without incurring any costs.
You should always get at least a ballpark estimate for your specific choices before making any financial commitment. You should not need to pay an additional fee for detailed drawings and general design consultations if you are purchasing their cabinets. Never hire a firm that insists all aspects of the work must be done through them. You will simply spend more without any benefit.
It is rare in this area that a general contractor is not hired to coordinate the many tradespersons you will need. A good, seasoned general contractor should have a network of skilled, reliable and reasonably priced subcontractors who come when needed and correct mistakes without drama. If the contractor insists on applying markups to all parts of the project including those that you alone are selecting and purchasing (appliances, decorative, materials, cabinets and counters for some examples), you should look further as this is not the standard or ethical practice.
A skilled interior design is sometimes employed as a sounding board for general concepts or to provide detailed specific recommendations for every surface in the kitchen. Chemistry, compatibility, their skill and your budget all come in to consideration here.