When should I use hyphens?

It's complicated. There are some rules but they are loose and they vary in different countries.

Here are three rules to help you along:

- hyphenate compound modifiers before nouns

- hyphenate between a word and a prefix if you want and if it looks better

- don't hyphenate two nouns that "belong together"

Hyphenate between a word and a prefix if you want and if it looks better

Never use a space for prefixes. You can hyphenate prefixes all the time if you want to. Some words are hard to read without hyphens, particularly when there are two vowels next to each other. In these cases you should always use a prefix.

Examples:

pre-historic or prehistoric

pre-diabetes or prediabetes

pre-existence (preexistance looks strange)

pre-industrial (preindustrial looks strange)

Don't hyphenate two nouns that belong together

In English, two words that belong together are not usually separated with a hyphen, they are separated with a space.

Examples: 

a tablet computer

the hospital food

a mobile phone or a cell phone
the biogas process

If the word really takes on a new meaning, it is often joined together as one word.

Examples:

smartphone or smart phone



Origin of the confusion:

In German, it used to be easy. Two nouns that belonged together would be stuck together. Donaudampfschiff. Now things are changing, and people are starting to use hyphens instead of putting words together, to give Donau-Dampf-Schiff. People think this comes from English, but you don't do this in English! It would be a Danube steamboat (a Danube-steam boat would be a boat that uses steam from the Danube, and a Danube steam-boat is just wrong).


P.S. There are always exceptions

Hyphenate compound modifiers before nouns

In British English, all compound adjectives should be hyphenated.

Example: 

a well-written article

nitrogen-fixing bacteria

In American English, it's not as important unless there is a loss of meaning without a hyphen.

Example:

a small-appliance company (company that sells small appliances)

a small appliance company (small company that sells appliances)

If it's not before a noun, it usually isn't hyphenated.

Example:

The advanced-physics teacher teaches advanced physics.

The text was very well written.

This website is quite useful.

do vs make

Correct use:

You do an activity, and you do any type of work.

For example: 

do an experiment
carry out an experiment

also, do a test, do/give a tour of the building, do/give a presentation,



Origin of the confusion:


In German it's all "machen", but in English, if you make something, you usually finish with a physical product.

For example: 

Make a cake, make a cup of coffee. 

There are several exceptions though, like make a plan or make up your mind.


More information: http://www.learnenglish.de/grammar/doormake.htm

shouldn’t or mustn’t vs don't have to

Correct use:

The term "you shouldn’t / mustn’t" means DON’T DO IT!
There is practically no difference between shouldn't and mustn't.

For example:

You shouldn't leave the door open at night.
You mustn't leave the oven on when you leave the house.
You should brush your teeth before going to bed.

Origin of the confusion:


The German term "du musst nicht"means "you don't have to".

For example:

You don't have to buy a ticket for the bus because it's included in your train ticket.

respectively

My advice: don't use this word.

This word can be confusing to many people. Really, it is quite simple. There is only one way to use it correctly. 

In the sentence: 

A and B relate to 1 and 2, respectively. 

A relates to 1. B relates to 2. This means that A does not relate to 1 and 2. A and B do not both relate to 1.


Example:

Increasing greenhouse gas emissions correlate with increasing and decreasing sea levels and polar ice coverage, respectively. 

The currencies of Japan and Russia are the yen and rouble, respectively.

Better still: don't use it!
Example:

Increasing greenhouse gas emissions correlate with increasing sea levels and decreasing polar ice coverage.

The currency of Japan is the yen and the currency of Russia is the rouble.

Origin of the confusion

1) It sounds good and people want to use it but they don't know how. 
2) In some languages a similar word (e.g.  "beziehungsweise" in German) means and/or. "Respectively" cannot be used to mean "and/or" in English.

E.g. 
"I will be late to the party, I should be there at 20:30 or possibly 21:00." 
"Ok, but don't forget to bring beer and/or wine!"

Present continuous or present simple?

Present continuous should be used when something is happening now for a limited amount of time.

For example:

Can I call you back later? I'm eating dinner.
Take an umbrella with you, it's raining.

Present simple is used for a fact (something that is always true) and for a routine.

For example: 

I have one sister.
I get up at 06:45 on weekdays.

The brewery in Vienna smells a bit like peanut butter.

Water boils at 100°C.

Present simple is used to describe results.

This shows that...
It indicates...
The sample consists of...

Origin of the confusion:
Present continuous doesn't really exist in German (ich bin dabei, etwas zu machen).  
Native German speakers who speak little English generally don't use present continuous. For example, if you asked "what are you doing" they might reply "I cook" (the correct answer is "I am cooking"). Or if you are talking in the cinema they might say "be quiet, the film starts" (the correct phrase is "be quiet, the film is starting").
Probably because they are afraid of making this mistake, native German speakers who speak good English generally use present continuous too much. They might say "your sister is looking a lot like you" (the correct phrase is "your sister looks a lot like you") or "I am sleeping a lot at the weekend" (the correct phrase is "I sleep a lot at the weekend").