En esta página una explicación con audio:
http://www.curso-ingles.com/gramatica-inglesa/compar.php
En esta página un montón de enlaces a ejercicios:
http://www.agendaweb.org/grammar/comparatives-intermediate-levelexercises.html
Comparison of Adjectives
When we want to compare two or more nouns using adjectives, we use the
comparative and superlative forms of the adjective to show the
comparison between the nouns. E.g. Honey is sweet, sugar is sweeter but victory is the sweetest.
In this sentence, we are comparing the three nouns using the positive,
comparative and superlative forms of the word ‘sweet’.
Positive Form These are the simple adjectives that simply describe the noun without
comparing it to another - big, sweet, clean, etc.
She has a big black dog.
He is a sweet boy.
The cupboard is clean.
Comparative Form These are used when we are comparing two nouns and need to show
which noun possesses the adjective or character in a greater or lesser
amount, when compared with the other. - bigger, sweeter, cleaner, etc.
I have a big dog but hers is bigger.
He is sweeter than the other boys.
The cupboard is cleaner than before.
Superlative Form This form is used when three or more nouns are being compared and we
need to show that one or more of the nouns posses the adjective or
characteristic to the highest amount possible. We usually add ‘the’ before
the superlative form. - biggest, sweetest, cleanest, etc.
She has the biggest dog in the colony.
He is the sweetest boy in his class.
The cupboard is the cleanest thing in the house.
Making Comparatives and Superlatives
There are certain rules that must be followed in the making of the
comparatives and superlatives of the adjectives. Not all adjectives form
their comparatives and superlatives in the same way and there are also
some irregular adjectives that form completely different comparative and
superlative forms.
Single Syllable Words and Double Syllable Words ending with -y, -er,
-ow, -le We use ‘-er’ to make the comparative and ‘-est’ to make the superlative.
Positive
Comparative
Superlative
Black
Blacker
Blackest
Fair
Fairer
Fairest
Clever
Cleverer
Cleverest
When there is a silent ‘e’ at the end of the positive form, we remove that
and add ‘-er’ and ‘-est’
Positive
Comparative
Superlative
Nice
Nicer
Nicest
Late
Later
Latest
When the adjective ends with a ‘y’, we convert the ‘y’ into ‘i’ before
adding ‘-er’ and ‘-est’
Positive
Comparative
Superlative
Pretty
Prettier
Prettiest
Lazy
Lazier
Laziest
If the adjective is a small one with little stress on the vowel, we double the
last consonant.
Positive
Comparative
Superlative
Hot
Hotter
Hottest
Wet
Wetter
Wettest
Other Words with Two or More Syllables For other double syllable words that do not end with -y, -er, -ow, -le, and
for adjectives with more than two syllables we use more and most to
form the comparatives and superlatives.
Positive
Comparative
Superlative
Difficult
More Difficult
Most Difficult
Careful
More Careful
Most Careful
Handsome
More Handsome
Most Handsome
Interesting
More Interesting
Most Interesting
Special Adjectives –
There a few adjectives that can use both ‘-er and -est’ and ‘more’ and
‘most’ to form their comparative and superlative forms. The distinction
between these is that ‘-er and -est’ are used when we are comparing the
noun to another noun and ‘more’ and ‘most’ is used when we are
comparing characteristics within the noun.
Positive
Clever
Quiet
Brave
Sure
Comparative
Cleverer/ More
Clever
Quieter/ More
Quiet
Braver/ More
Brave
Surer/ More
Sure
Irregular Comparisons –
Superlative
Example
Cleverest/Most
Clever
He is cleverer than
her.
He is more clever
than studious.
Quietest/ Most
Quiet
This is the most quiet
it gets here.
This is the quietest
place.
Bravest/ Most
Brave
She is braver than
other girls.
She was more brave
than afraid.
Surest/ Most
Sure
He was surer of the
result than others.
You’ll be more sure
about the concept
after you read the
chapter.
These adjectives do not make their comparative and superlative forms
using the rules above. Their comparative and superlative forms are
different words altogether.
Positive
Comparative
Superlative
Bad
Worse
Worst
Good
Better
Best
Far (place & time)
Further
Furthest
Far (place)
Farther
Farthest
Old (people)
Elder
Eldest
Little (amount)
Less
Least
Late (order)
Latter
Last
http://www.englishleap.com/grammar/comparative-superlative
Adverbs.
With LY adverbs (adverbs formed from adjectives by adding -ly to the end) we form the
comparative and superlative forms with more and most.
Adjective Adverb Comparative Adverb Superlative Adverb
quiet
quietly
more quietly
most quietly
careful
carefully more carefully
most carefully
happy
happily more happily
most happily

Jeff works more quietly than Steve does.

Jeff works the most quietly of all the students.

Mary drives more carefully than John does.

Of the three drivers, Mary drives the most carefully.

Steve works more happily than he used to.

Mary sings the most happily of all the girls in the group.
Other Adverbs.
For adverbs which retain the same form as the adjective form, we add -er to form the comparative
and -est to form the superlative.
Adjective Adverb Comparative Adverb Superlative Adverb
hard
hard
harder
hardest
fast
fast
faster
fastest
early
early
earlier
earliest

Please work harder.

Steve works the hardest.

Mary runs faster than John does.

Mary runs the fastest of all the runners on the team.

Steve gets to work earlier than I do.

Steve gets to work the earliest of all.
Irregular Adverbs.
Adjective Adverb Comparative Adverb Superlative Adverb
good
well
better
best
bad
badly
worse
worst
far
far
farther/further
farthest/furthest

John plays tennis better than Jack does.

On our tennis team, John plays tennis the best.

I did worse on the test than Bart did.

On that test, I did the worst in the class.

My paper airplane flew farther than yours did.

My paper airplane flew the farthest of all.
http://www.eflnet.com/tutorials/advcompsup.php