Links are to Amazon. Obviously, use the bookseller of your choice.
Practiceopedia, Philip Johnston
Want to practice better and more efficiently? This book has thousands of practice hints and ideas to make more of your time at the piano. Aimed at students
The Practice Revolution, Philip Johnston
Ideas and guides for more efficient and enjoyable practice. Aimed at older students, parents, and teachers.
Helping Parents Practice: Ideas for Making it Easier, Edmund Sprunger
A bit more academic than the Johnston books. Lots of ideas for parents who need help helping their child practice.