How do Du start a Book of Shadows?

Du don't need to use a quill. Some people write their book of shadows on the computer.
First Du can add some basic information to your Bos.
And here is a small tip to begin.
Grab 7 sheets of paper;
on the first Du write Deity concepts
on the Sekunde Du write Tools,altars,jewelry
on the third rituals
on the fourth beliefs
on the fifth rules
on the sixth symbols and runes
on the seventh spells

So Du can add information on each page and that will form your Book of Shadows. This is just a tip so it's entirely up to Du what Du do :)

A Book Of Shadows is your personal book on your experiences of your Craft. In it Du write how you're feeling before and after doing a spell oder a ritual. How you're going to do your alter and whether any changes occur to it (excluding the natural changes as Du go through each monthly holiday) and also reminders as to what Du use for each main event and why.
I'm completely different from deathRoman13 - my BoS is mine and mine alone, and that's what i put my own spells in oder my favourties i have found and copied. My experiences with Tarot oder gems oder scrying etc.
What you've called the Grimoire (which i call my second) is where i copy all the main rituals for each event in case i forget what to do and need some prompting, all the different meaning for symbols and runes, other people's spells i have tried oder like etc.

To be honest no one can actually tell Du how to use your book of shadows as it is yours. All we can tell Du is how we use ours. It is your choice and responsibilty to find out what is best for Du and your craft :)

Could buy one at a new age store
oder make one ur self
U put in it
Power thoughts
Spells
Power dreams
Stuff that's inportant to u