Adjectives and Adverbs

Adjective is a word or set of words that modifies a noun or pronoun. Adjectives may come before the word they modify.
Example:
That is a cute cat.

Adjectives may also follow the word they modify.
Example: That cat looks cute.

An adverbis a wod or set of words that modifies verbs, adjectives, or other adverbs.
Example: 
He walks slowly (modifies the verb walks)
He is especially bore (modifies the adjective bore)

An adverb answers how, when, where, or to what extent-how often or how much.
Example:
He walks slowly (answer the question how)


Rule 1
Many adverbs end in -ly, but many do not. Generally, if a word can have -ly added to its adjective form, place it there to form an adverb.
Example:
She thinks quick/quickly
How does she think? Quickly

She is a quick/quickly thinker.
quick is an adjective describing thinker, so no -ly is attached.

Rule 2
Adverbs that answer the qustions how sometimes cause grammatical problems. It can be a challenge to determine if -ly should be attached. Avoid the trap of -ly with linking verbs, such as taste, smell, look, feel, etc., that pertain to the senses. Adverbs are often misplaced in such sentences, which require adjectives instead.
Example:
Roses smell sweet/sweetly
Do the roses actively smell with noses? no; in this case, smell is a linking verb-which requires an adjective to modify roses-so no -ly.

Rule 3
The word good is an adjective, whose adverb equivalent is well.
Example:
You did a good job.
Good describes the job.

You smell good today.
Good describes your fragnance, not how you smell with your nose, so using the adjectives is correct.

You smell well for someone with a cold.
You are actively smelling with your nose here, so use the adverb.

Rule 4
The word well can be an adjective, too. when reffering to health, we often use well rather than good.
Example:
You do not look well today.
i don't feel well, either.

Rule 5
Adjectives come in three forms, also called dgrees. An adjective in its normal or usual form is called a possitive degree adjective. There are also the comparative and superlative degrees, which are used for comparison, as in the following.
Example:
Possitive             Comparative                  Superlative
  Sweet                  Sweeter                       Sweetest
    bad                     Worse                          Worst
  Efficient            More efficient                Mose efficient

A common error in using adjectives and adverbs arises from using the wrong form of comparison. To compare two things, always use a comparative adjective:
Example:
She is the cleverer of the two women (never cleverest)
Trhe word cleverest is what is called the superlative form of clever.

Rule 6
There are also three degrees of adverbs. In formal usage, do not drop the -ly from an adverb when using the comparative form.
Incorrect: She spoke quicker than he did.
Correct: She spoke more quickly than he did.
Incorrect: Talk quieter.

Rule 7
When this, that, these, and those are followed by a noun, they are adjectives. When they appear without a noun following them, they are pronouns.
Example:
This house is for sale
This is an adjective.

This is for sale
This is a pronoun.


Sumber:
http://www.grammarbook.com/grammar/adjAdv.asp