1/2 cup all-purpose flour
2 cups cold water
2 cups boiling water (requires adult supervision)
3 tbsp. sugar

Mix together flour and cold water in a bowl.
Add this mixture to the boiling water and allow it to return to a boil.
Remove from heat and stir in the sugar.
As the mixture cools it will thicken as it does.
You can also just make a quicky paste by putting flour in a bowl and adding water until you have kind of a soupy paste.
If you're planning to make something you want to last for years and years, be aware that flour paste can get moldy, especially in humid environments.
You might want to try using powdered wall paper adhesive (non-pourous) mixed with water.
It comes in milk carton type containers and you can find it anywhere wallpaper is sold.
Be sure to cover your work area with lots of newspaper or wax paper - papier mache can get very messy!

Tear (don't cut) narrow strips of newspaper or newsprint.
Narrower strips work best when using a rounded mold... for flat or rectangular surfaces, larger strips are ok.
Dip the strips into the paste, coating completely.
As you lift the strip out, run it between your thumb and forefinger to squeeze out excess paste.
Then drape the strip across your mold. Overlap strips slightly as you go - the torn edges will blend together and your final product will have a smoother finish.
You may need more than one layer of paper.
It's best to allow each layer to dry before putting another on - this means some projects could take several days!