I am a charity shop volunteer. We are grateful for anything, just ask yourself first whether you'd pay money for it. That colouring book with scribbles on every page and the empty DVD boxes are really just fit for the bin.
A few pointers on other stuff:
Textiles - we will take ANY FABRIC ITEMS and those which aren't fit for sale we will send for rags. We will love you forever if you mark bags as rags. Bedding - duvet covers might sell in good condition, sheets generally don't and we'll rag them. 70s blankets, curtains and bedding flies off the shelves as people look at them in terms of the fabric content rather than the item itself. We can also recycle shoes, belts and bags.
Electricals - we can't take anything which plugs into the mains, other places can. Always ask first.
Food - we can't sell any donations which are edible. Even if it's one of those "cook Japanese" kits with a wok, chopsticks and rice. We'd have to throw the rice out, and just sell the non-edibles.
Toiletries - unused and unopened make-up, gift sets, and all other toiletries sell well. So does wrapped soap. Anything opened has to be binned.
Fur/Angora - the charity I volunteer with has a policy not to sell anything with fur or made from angora. It goes for rags. Other charities may have different policies.
Video tapes and cassettes - pretty much obsolete and impossible to shift. Unless it;s something really, really special.
Things which sell well in my experience:
craft stuff
homewares - especially retro 70s/80s
jewellery - especially clip earrings
Lego and jigsaws, board games in good condition
Books - both reference and modern paperbacks
Vinyl music (CDs not so much)
Coats, jackets, occasion wear, high end brands like Hobbs, Reiss, Toast.
Christmas decorations and baubles