Magic Forums

My name is Cirrus, and I am new to the site (as you may have guessed). After looking through Newbie Central, I still have some questions that I feel weren't quite answered.
A. Covens: I'm interested in seriously pursuing magick, but I'm not quite sure where to start. I gathered that Covens are basically community groups of people with the similar interests, but how do I choose a coven to apply to? Can you join multiple Covens at once? And once you join, are you totally committed to it?
B. How can I determine what spells are real and which are not? Example: I wish to write/ copy down my own physical spellbook with my experiences and spells in it. I thought that a good spell to start with would be a protection spell over the book to protect my privacy and help keep anyone who would disapprove unaware of my practices. A search through the online spellbook brought up 4+ different spells to that end. How do I know which one works? Or is it simply a matter of my intents and belief that a given spell will work?

ANy help would be greatly appreciated!