1. The Superlative

2. The Superlative of adjectives in English.
To form the superlative of an adjective, English adds -est ("prettiest") or uses most ("most beautiful").
Examples:
Adjective Comparative Superlative
nice nicer nicest
Interesting more interesting most interesting
handsome more handsome most handsome

3. The Superlative of adjectives in German.
One way to form the superlative in German is with am + adjective + sten.  
Examples:
Adjective Comparative Superlative
schnell (fast) schneller (faster) am schnellsten (fastest)
traurig (sad) trauriger (sadder) am traurigsten (saddest)
jung (young) jünger (younger) am jüngsten (youngest)

4. When the adjective or adverb ends in a d, t or s sound, an e is inserted between the stem and ending (am grössten is an exception.)
Adjective Comparative Superlative
kalt (cold) kälter (colder) am kältesten (coldest)
alt (old) älter (older) am ältesten (oldest)
intelligent intelligenter am intelligentesten (most intelligent)

5. Some irregular forms also exist:
Adjective Comparative Superlative
gern (gladly) lieber (rather) am liebsten (most rather)
gut (good) besser (better) am besten (best)
hoch (high) höher (higher) am höchsten (highest)
nah (near) näher (nearer) am nächsten (nearest)
viel (much) mehr (more) am meisten (most)

6. Another way to form the superlative is to add an ste ending to the adjective.
Adjective Comparative Superlative
schnell (fast) schneller (faster) schnellste (fastest)
schlimm(bad) schlimmer (worse) schlimmste (worst)
blau (blue) blauer (bluer) blauste (bluest)
jung (young) jünger (younger) jüngste (youngest)
traurig (sad) trauriger (sadder) traurigste (saddest)
Er ist der jüngste Student in der Schule.
Er ist der jüngste.

7. When using this method, if the adjective ends in a t
When using this method, if the adjective ends in a t. Then you must add an extra e before you add the ste ending.
Adjective Comparative Superlative
alt (old) älter (older) älteste (oldest)
kalt (cold) kälter (colder) kälteste (coldest)
schlecht (bad) schlechter (worse) schlecteste (worst)
Er ist der älteste in der Klasse.
Er ist der älteste.