I kind of wrote a cookbook. I put together a privately published cookbook for a large company that was used for their corporate christmas gift.
There are many things to be aware of: what is your market? This will influence what kind of recipes you include and what level of instruction you provide.
You have to decide on the format of the recipes and what kind of mesurements you will use, and make sure these are consistent.
Get yourself good proof readers (probably provided by the publisher, which is another thing you need)
If you are unknowen to publishers you may have to basically write part or whole of the book and then shop it around. They don't normally give contracts or advances if you haven't done a succesful book before.
Have you been asked to write a book or do you just want to write one?
What are your ideas as to theme or content?
I'm interested to know your situation b/c there are so many different variables to different books.
write more, good luck.