Kyle Bennett, Spiritual Disciplines for the Life of the World
Richard Foster, Celebration of Discipline
Pay attention to what you buy and practice not buying more than you need. This can apply to clothes, food, tools, books, and so much more.
Rather than buying, borrow what you can of things that you do not need to own. For example, if there is a book that you want to read, see if it is in the library before you choose to buy it. This can also apply to things that you would use for a particular job that only comes up once in a while; for example, if you have a hedge that needs trimmed in your yard, rather than going out and buying a hedge trimmer, see if you can borrow one from a neighbour.
Have a look though your home: are there things you own that you have not used for some time? Consider giving those items away to someone who could use them.
Limit your choices (how many T.V channels do you really need? pairs of shoes? kinds of cereal?)
Simplicity: A Practical Guide by Adele Calhoun
Simplicity: Inward and Then Outward (Podcast) by Nathan and Richard Foster