Two books I would recommend purchasing to help you along:
Advanced trade secrets of professional landscape lighting: by Nate Mullen
(This is an introductory book to give you the basics of getting started into landscape lighting- some of the material is outdated but the book is relevant overall)
The Landscape lighting book: by Janet Moyer
(This is a more advanced read for someone once they have a general knowledge of lighting and lighting design already)
Of course this forum has some pretty deep archives with a wealth of information in them also. General searches on topics should uncover some very helpful tips for you.
One of the best ways to learn about design and light characteristics is to buy some equipment and experiment around your home or a friends by setting up some various mock-ups and see the effects first hand as you move the equipment around into different scenarios.
Good luck, once you get into doing lighting- you will be hooked.