Who/whom I/me
In spoken English it is probably not very important if speakers confuse subjects (who, I) with objects (whom, me). In writing - unless there are reasons for imitating a spoken idiom - it is probably more important to get it right:
between you and me (prepositions govern the object)
With who/whom the position is more complicated. Quite often the use of whom as a relative pronoun is unnecessary anyway:
He is a man (whom ) I admire.
Whom is never used with the verb to be because the verb to be cannot take an object:
Are you who I think you are? (Not :Are you whom I think you are?)
If whom is embedded in a sentence in such a way that it appears to be the object of an inserted verb, there is often confusion over its real grammatical function:
She's the person whom we hope will win the contest.
Here the whom is incorrect because it is not the object of hope but the subject of win (She is the person who [we hope] will win the contest).
Each, every, every one, everyone, either, neither, none
These words are singular forms and should, therefore, take singular verbs: Each of the children want their share.
Technically this should be:
Each of the children wants his or her share. Other problems with agreement
Singular subjects require singular verbs; plural subjects require plural verbs. Problems arise when a noun that is not its subject precedes the verb and confuses the issue:
The contract binding the parties and their dependants were clearly difficult to enforce. (Here the subject of the verb to be is contract, so the verb should be singular: was clearly difficult to enforce.)
Two linked units might be regarded as either separate or combined into a single unit:
Law and order has/have been restored.
Comparisons and superlatives
When two things only are being compared, use the comparative form:
She is the more elegant of the two sisters. (Not: she is the most elegant of the two sisters.)
Less and fewer
Less refers to quantity and fewer to number:
I would like less sugar and fewer cakes.
Placing adverbs
Only, even
In formal writing these words should be placed next to the word they concern, although in spoken English they tend to be placed next to the verb.
Consider the possible meanings of the following sentence if only is moved:
At home I only drink coffee in the morning.
