Which hook to use

I am very new to developing plugins and I am wondering if I am going about this the right way. I want to create an item and save the changes to populate in the database for the admin side. Am I right in thinking that I should add a function to “admin-init” and check the $_POST values generated by the form and then process depending on the values. What I notice that is “admin-init” runs every time an admin page is called – is there a hook that can be used for a particular menu item?