Adverb or Adjective - Which should I use?

Adverb or Adjective - Which should I use?
From Kenneth Beare

Adjectives Modify Nouns
Adjectives are placed directly before a noun:
Examples:
Tom is an excellent singer.
I bought a comfortable chair.
She's thinking about buying a new house.

Adjectives are also used in simple sentences with the verb 'to be'. In this case, the adjective describes the subject of the sentence:
Examples:
Jack is happy.
Peter was very tired.
Mary'll be excited when you tell her.

Adverbs
Adverbs Modify Verbs, Adjectives and Other Adverbs
Adverbs are easily recognized because they end in '-ly' (with a few exceptions!):
Examples:
Adjective - careful / Adverb - carefully
Adjective - quick / Adverb - quickly

Adverbs are often used at the end of a sentence to modify the verb:
Examples:
Jack drove carelessly.
Tom played the match intelligently.
Jason talks about his classes constantly.