BETTER SHIT TO PUT IN YOUR GRIMOIRES THAN THE BASIC SHIT EVERYONE SAYS:
Maps! Maps! MAPS! If you're a death witch, get one for the cemeteries you visit and mark gravestones/areas you've practiced in! Garden witches! Map out your gardens! Green witches! Map where you find specific herbs in your area! Lunar witches! Mark the best spots to go look at the sky! Make a key! Take notes!
Recipes for COMPONENTS! Write down how to make the mixtures you use in spells often- A special salt mixed with herbs and put under the moon, a mixture of oils for protection, the herb mixes sachets you keep making to add to sachets, whatever!
For green witches- press samples of stuff and glue them in! Go to an arboretum and ask for permission to take leaves to press, they'll usually let you take some- add them in with your notes about trees
Cool ways to make spells! I make spells in envelopes and on empty spools, what are some ways you do?
The local plants in your area and what they do. You're not going to be likely to find chrysanthemums to forage in Missouri, but you will find creeping charlie and prairie plants. What can you do with a thistle?
When you celebrate a sabbat, write down what you did and include samples! Ribbons from your Beltane altar, a pressed sample of your lemmas harvest, a scrap of your Yule decorations. Maybe do a spell and tape the remnants into your grimoire in a plastic baggie
Learn how to make an envelope out of paper just by folding it, how to string seeds, how to dry plants, how to macrame rocks and hang them from your window. Find those little witchy skills and write them down.
How to incorporate your hobby into your magic. Sigiling origami paper, weaving knot magick into your crochet, making blessed bookmarks, etc
Substitutes! Rosemary, rose and clear quartz are good for most things, but there are more substitutes to be used that are more powerful. Roanoke bells are good substitutes for bluebells, apparently.
Correspondences of odd things. Turns out different kinds of cats have different correspondences, huh.
Superstitions and such from where you're from.
For kitchen witches: easy to alter recipes. An egg noodle recipe that takes herbs really well, a simple bread recipe that can be dressed up for spells or rituals, how to make a good pie crust that you can sprinkle nutmeg in or whatever you desire.
Or: What foods go good with what herbs. You'll make a better apple pie (and get the benefits of apples, nutmeg, and cinnamon together!) If you know how your herbs taste together with your cooking. (Most kitchen witches know this stuff, but for a green witch who likes to make teas or a sea witch that likes to make soup, etc, this is important)