When used separately, many people have no problem using the correct word:

• When you’ve finished, can you email the report to Ivan?
• When you've finished, can you email the report to me?

The problem arises when both are used in the same sentence:

• When you’ve finished that lab report, can you email it to Ivan and I?

The above sentence is incorrect, as I is a subject pronoun. Ivan and me are object pronouns and these should be used:

• When you’ve finished that lab report, can you email it to Ivan and me?

If you are not sure, remove the proper noun (Ivan) and we can see the sentence is not correct (When you’ve finished that lab report, can you email it to I); therefore, we know me is the correct pronoun.

Who and that is frequently used interchangeably:

• I have a friend who can help us.
• I have a friend that can help us.

However, when we are referring to a person, we use who:

• It’s John who’s coming to the meeting not Henry.
  

When we are referring to an object, we use that:

• This is the report that I was talking about.

When people say I have a friend that can help us it is informal and should not be used when writing.

We use how and what to request information. We use how to ask about the way or manner, or by what means:   

•  How are you?
•  How did you get here?
•  How do you pronounce his name?

 
 We use what to ask for information when specifying something:

•  What does she look like?
  
•  What do you call this?

We do not need to use the definite article when referring to something in general or non-specific:

• Worry kills women more than work. [not the women]

 
We do not need to use the when referring to non-specific mass nouns:
 

• Water on the floor is dangerous and should be cleaned immediately. [generally, water on the floor is dangerous: water is non-specific]
  
• The air should be filtered twice every hour for every ten persons. [recommendation for an air filter setting: specifying air through the filter, not air in general]
  

News is a mass or uncountable noun, so we do not use the indefinite article (or determiner) a. If we want to refer to one news item, we can use item or piece:
 

• I have a particular item of news to tell you.  
• I have a piece of news that might interest you, Mr. Holmes.

However, we usually say:

• I have some news for you, Mr Holmes.
  

Into and in to are frequently confused.

Into is a preposition which expresses movement e.g. Let’s move into the dining room.  We normally use into after verbs suggesting change:

• I need to go into the bank. [need does not express change but the preposition does]
• I need to go in to the bank.
• Can you translate this into Catalan and Spanish? [in + to would be incorrect].
• Can you change these euros into dollars?
  

Although they are pronounced the same, they have very different meanings.

As a verb, complement means add to something in a way that enhances or improves:

• That coat complements your hat beautifully.
  

Compliment means to admire and praise someone for something:

• Fred complimented me on my negotiation skills.
  

Between is used to refer to two or more things which are clearly separated:

• Stand between the red lines.

Among/ amongst is used to refer to things situated more or less centrally in relation to several other things:

• There was a small cottage amongst the trees, deep in the woods.

[Amongst is UK English]

We use fewer with countable nouns and less with uncountable or mass nouns:

• We sold fewer cakes this month compared to the same time last year.
• The fewer words she says the better.
• We’ve got less money than I thought but I don’t know why.
• The less said, the better.

Less is normally used with numerals:

• She had a score of less than 100.

and with expressions of measurement or time:

• He worked here for less than two weeks.
• We live less than four miles away.

but fewer is used if the things denoted by the number are seen as individual items or units:

• There were fewer than ten candidates for the position.
  

We use:

• e.g. to mean for example
• i.e. that is to say and is used to add explanatory information or to state something in different words:

• There are many types of material from which shoes can be made e.g. leather, plastic, cotton.
• It’s a new type of shoe made from laboratory enhanced organic polymer, i.e. a synthetic leather.