If it has feet, I will let is stand on the ground. And no, I'd never eat in a place with dirty floors (what will the food be like if they can't keep the floors clean?!)
If it can sit next to me on a chair or the likes of a chair, I will prefer to put it there.
If it has a long strap, i will hang it on the back of my chair, and if all else fails, i will keep it in my lap!!