"The girl reads a good newspaper."
Translation:La fille lit un bon journal.
Some adjectives go before, others go after. Check here: http://french.about.com/od/grammar/a/adjectives_4.htm
There is a good rule of thumb B.A.G.S. which is Beauty, Age Goodness and Size. If an adjective goes into one of these categories it goes before the noun, otherwise it typically goes after the noun. "Bon" is a measure of how good something is so it goes before the noun.