In Cultivating Chaos: How to Enrich Landscapes with Self-Seeding Plants (Timber Press, 2015), German garden editor Jonas Reif, nurseryman Christian Kress and photographer Jurgen Becker take you through all the steps to planting species that will seed around without crowding out the plants you want to survive.
In the introduction, British designer and author Noel Kingsbury says that allowing plants to self-seed in the garden and spread themselves around "is part of the new garden zeitgeist....Gardening now is much more accepting of spontaneity, of natural processes of birth, death and decay."
The authors explain the general philosophy of designing with self-seeding plants, profile successful self-seeded gardens, give you the garden basics of planting and seeding, and finally, outline strategies for design and maintenance. Toward the back of the book, they list plants suitable for masonry joints, gravel beds, those that are best for flower borders, and species that do best in sun and in shade.
I've had good luck myself with some plants that seed around ... this book makes it easy to have a low-maintenance garden (at least in some parts of the yard) ... and takes out the mystery of how to do it.