An inexpensive bamboo roll-up window shade works fine, and there's always aluminum foil. Keep the sun from actually hitting the windows to lower the heat building. Don't forget the doors. The best choice for your wall shade is vegetation. Although it takes many years to grow a tall tree, vines grow in just a few weeks.
Morning glories provide plenty of shade plus flowers that are beautiful to look at.
There are many varieties of pole beans which will climb right up your walls as well as cover windows. Hang some twine down the wall for each plant to assist their climb, or put up a trellis or some cheap chicken wire. Switch from incandescent lights to flourescent. Don't use overhead lights when a table lamp will do. Use less lighting during the day when natural light is available.