Common Mistakes : Each other

pronoun

.BAD: I hope that you will both write to each others
.GOOD: I hope that you will both write to each other

: Each other has no plural form
.We’ve been writing letters to each other for the last two years

.BAD: We had to describe the pictures each other
.GOOD: We had to describe the pictures to each other

.BAD: They live a long way each other
.GOOD: They live a long way from each other

You use prepositions in front of each other (pronoun) in the same way as you use prepositions in front of him, her, us etc
:Compare
.We talked to her
.We talked to each other