Just like your regular kitchen, the one in your backyard needs the be carefully planned before you start to build it.
First, think about the basics. Will the outdoor kitchen be on the deck or the patio? Next to the house or out in the yard?
Next, you need to get an idea of how much space to allow, How often will you use the outdoor kitchen? How many people will you be cooking for? Is your plan to entertain large groups or just a few friends and family? Will the kitchen be used to prepare full course meals or just quick and small dinners?
For example: if you're only planning to barbeque, then you may not need to have a stove top. On the other hand, if you plan to cook sauces or steam vegetables while the meat is grilling, you should consider a stove top.
Do you want a refrigerator outside to keep your meat and other food close at hand? Or just to keep your beverages cold? If the perishable food is kept inside the house then you can probably get by with a small refrigerator outside.
If electrical appliances are part of your backyard kitchen plans, you'll need to determine what type of power you will need. If you already have outdoor outlets, maybe you can plug the appliances into the existing power. If the kitchen is located away from the house, you will probably need to run underground cable.
Plan and lay out your design on a piece of graph paper. Measure your own kitchen so you can get a feel for what kind of space you'll need. For inspiration, plans, and guidelines you'll want to get a solid book before you start.
Make sure you factor in exactly what kind of cooking you'll be doing and leave some room for expansion. For example: if you're only barbecuing then you don't need a stove top, but maybe you should consider a stove top for creating sauces, etc.
Do you need a refrigerator outside to hold your meats and veggies and such? Or just to hold a few sodas? If all the food is stored in the house (a good idea in many areas) then you can easily make do with a small fridge.
Will you be doing the food prep outdoors? If so you'll want a sink and will need the appropriate plumbing hookups. Safe handling of food is just as important when barbequing as when you are cooking in your own house.
What kind of storage do you want? Will you have a dedicated outdoor set of dishes or just carry dishes and cookware from the house?
Are you going to have an indoor or outdoor eating area? Will it be covered by a roof extension or a patio canopy or a gazebo in case of rain?
Do a physical layout of your outdoor kitchen with chalk or string, and get a feel for size and what goes where. This is the time to really think about the details. Jot down all your thoughts in a notebook.
If you're going to be adding any power or plumbing or permanent structures, then pay a visit to your local building department to see whether any permits are required. If you are running new electricity or plumbing, there is a good chance permits are required. Keeping your project legal can help to avoid problems later. An illegal outdoor might have to be ripped out. Also, the inspections just might catch something that needs to be fixed, such as a wrong power hookup.
With a little planning you can create an outdoor kitchen which will give you years of enjoyment in your own outdoor oasis.