Well, I haven't yet graduated to a fully blown kneeboard, not having started navexes! But I do have a chart which I put down beside the seat and a plasticised piece of paper strapped on my knee for ATC instructions.
I keep the following useful stuff in my grow-bag: Two pens, Chinagraph pencil, torch, local area chart, sunglasses, mobile, car and house keys and ID (i've got a story about why I carry that which I won't bore with).