1.think over为动副结构,侧重于思考,不涉及结果,表达“深思熟虑,仔细思考”之意；
eg.The whole night she was thinking over the problem.
2.think about,表示“考虑”特别是考虑某一计划是否可行,后接一个名词、动名词或带疑问词的不定式.
eg.I promise you I"ll think about your suggestion.
3.think of主要表示“考虑,关心,想起,对……有某种看法”之意,为动介（动词十介词）结构.表示看法、评价之时,常用一些副词来修饰,如think much／a lot／a great deal／highly／well／ill of…（对……评价高／好／不好）；若问评价如何,觉得怎样,常用what…think of…
eg.She thinks of the whole thing as a big lie.