The place to start when you are designing your dream kitchen is with a dimensional diagram of your kitchen space. On a large piece of graph paper, draw the outline of the kitchen space, including any doors or windows that you will have work around while you design your kitchen. Accurately mark where your plumbing and electrical supplies are located. You can move plumbing and electrical supply points, but this involves more time and money, and it is always easier to accommodate existing service supplies into your design, if practical.
Tying the whole kitchen together will be your countertop and backsplash selections. You have many options of materials, colors, and textures to choose from that this decision can become quite daunting. Your kitchen designer will be able to sort through all of the options, and help you to pull every design item in your kitchen into a coherent unit. While you are deciding on the features in your kitchen, the designer can be making changes on their computer to show you exactly what the design changes will look like in your finished kitchen. Maybe two great design items that are stunning individually, may not work well together, and seeing this on a computer screen can help you avoid making a poor decision, that you will regret later.