The most common adjectives come before the noun.

grand (big, tall) petit (small)  
bon (good) mauvais (bad) meilleur (better)
jeune (young) vieux (old)  

autre (other)
beau (beautiful)
faux (false, fake)
gros (large, fat)
haut (high, tall)
joli (pretty)
même (same)
nouveau (new)

These adjectives are different because they are perhaps the most basic, important adjectives in the language. They have special status. In fact, you can write simple sentences based almost entirely on these adjectives

[Examples with cartoons - under construction]

In case you're unimpressed by the cartoons, French teachers have come up with a snappy little mnemonic device that you can use to help you learn these adjectives instead. It's called BAGS.

Beauty beau, joli
Age vieux, jeune, nouveau
Goodness bon, mauvais, meilleur
Size grand, petit, court, long, gros, haut

'Autre' and 'faux'' (and the other less common adjectives that also usually come before the noun) just tag along for the ride.

Don't make the mistake, though, of thinking all adjectives describing any of the these four characteristics come before the noun! Only those listed do that.