A good one lays out the ingredients and walks you through the steps, and if it's for beginners, explains the details of how to get the ingredients if necessary.
A more typical one is the series of notes the wizard took to jog his memory, vague to the point of being useless to others.
Historically, cookbooks, although intended for others, were intended for other professional cooks who already knew all the basics and just needed to be told to apply them to a new recipe. Not to mention the vague measurements. Fannie Farmer's cookbook was the first one to include such rules as "a cup of flour is measured level." Then, it was the first book intended for people who hadn't boiled water before.
One wonders where there would be a similar progression in spell books. With the added factor that the early ones might be encoded, as alchemic texts were, for safety and to keep secrets.