Your budget and priorities will help you determine which type of appliances you will purchase.
It is recommended to use the same appliance brand for all your appliances if possible, but this is not a must. You may want to look into the style and functionality which you prefer, because this will help determine your appliance selection.
Since the fridge is the appliance which is most frequently used, quite often this is where you may want to consider an upgrade. You should also decide on the overall size you will need (24, 30, 36, 42 and 48 inches are typical sizes)
Your first big choice about your refrigerator is whether or not you want it to be built in or free standing.
Built in refrigerators are significantly more expensive than free standing fridges.
Next you should decide if you want a range which is one appliance for both the oven and the cooktop or do you prefer the look and feel of a separate built in oven and built in cooktop.
Keep in mind that usually a built in oven will require a dedicated 220 Volt electric line
You should also decide if you prefer to cook on gas or electric/ induction. For your oven and cooktop you should decide what is your preferred dimension (24, 30, 36 and 48 inches are typical).
For your sink you should mainly decide on your preferred sink size based on your design preference and space availability.
The rest of the items are easier to select and depend mainly on your budget and style preference.
You will need to decide if you will use an exposed or built in hood, same with a dishwasher, do you need a microwave or not? Coffer maker, steam oven, wine cooler, ice maker, separate freezer, warming drawer?
Once you have made some selections you should work with your kitchen designer in order to determine the exact sizes and brand.