Book knowledge is the ability to recognize book formats and purpose. Early readers learn how to hold a book properly, to read English from left to right, how pictures supplement the story, and that books have basic components such as a front and back, spine, pages, covers, and more. Children automatically learn these things at a conceptual level long before they understand the purpose of each component.
By the time your child is ready for kindergarten or school, they should be able to recognize their own name and other simple written words. The sounds of each letter of the alphabet should be familiar to your child, and they should understand the principle of reading from left to right, which way to hold a book, and possibly even be starting to read three and four-letter words.
When your child is ready, move on to pencil and paper. Build confidence by letting your preschooler trace simple lines and shapes, then proceed to letters. You can eventually teach your child to write his name by letting him trace or copy it daily. If your child needs help remembering how to spell her name, practice with fridge magnets, letter tiles or alphabet blocks.
Do choose worksheets that are appropriate for the child's level, since children can get discouraged easily, if they are unable to perform the activity. Well illustrated worksheets with cartoons are also more likely to appeal to children. Worksheets that use common situations children come across at home, school, in the market place etc and that use common objects known to children would be more relevant.