1．比较对象是否明确
比较必须在同类事物之间进行，用that代替天气和人口。如：
My pen is better than yours.
The weather of Harbin is colder than that of Beijing.
2．比较的范围
比较级中的被比对象与比较对象必须属于互不分离的两个范围。比较的对象如在同一范围内。必须加other一词，将比较的个体排除在外。范围内加any other 范围外加any.
He is taller than any other boy in his class.
Canada is larger than any country in Asia.
3．比较级前的修饰语
常用来修饰比较级的词有：much ,a little , a bit ,a lot ,even ,still ,a great deal of, far ,by far ,any ,rather
及表示倍数的词。修饰可数名词用：many more或few.修饰不可数名词用：much more .
There are many more books in your library than in ours.
His handwriting is much better than mine.
4．比较状语从句中的省略
than后是一个完整的句子，有时为了避免重复，把谓语部分省略。但如果前后时态不同，则不能省略。
The book is more interesting than that one (is interesting).
She is much taller than she was last year.
I think he will be more careful with his study than he is now.
5．比较级与冠词the的使用
表示两者中比较的一个，要用( the + 比较级 + of the two)的句式.
He is the stronger of the two boys.
English is the easier language of the two.
6．表示倍数的三个结构
1 )be + 倍数 + as as
2 )be + 倍数 + 比较级 +than
3 )be + 倍数 + the +名词(尺寸，长度)+of
The house is three times as big as that one .
The house is three times bigger than that one .
The pencil is twice the length of that one
7．比较级 + and + 比较级 越来越
Days are getting longer and longer.
8．the + 比较级 ，the + 比较级 越，越
The more ,the better.
The more you eat, the fatter youll be.
9．the + 序数词 + 最高级 +
Which is the first most useful invention ?
10．one of + 最高级+ 名次复数
He is one of the tallest boys in his class.
11．由物主代词修饰的时候，不用冠词
He is my best friend.
特殊比较级的构成：
原形比较级最高级备注
farFarther / furtherFarthest / furthest
Many / muchmoremost
Good / wellbetterBest
oldOlder / elderOldest / eldest
littleLessLeast
Bad / badly / illWorseWorst
importantMore importantMost important多音节形容词和副词