Articles: a/an, the, no article

Use a / an with singular countable nouns.
The first time you mention a thing/person. I saw an old man with a dog.
When you say what something is. It's a nice day.
When you say that somebody knows. She's a lawyer.
In exclamations with What...! What a wonderful day!
In expressions like... three times a week

Use the
When we talk about something we've already mentioned. I saw an old man with a dog, and the dog was barking.
When there's only one of something. The moon goes round the earth.
When it's clear what you're referring to. He opened the door.
With places in a town. I'm going to the theater.
With superlatives. It's the best restaurant in town.

Don't use the
When you are speaking in general (with plural and uncountable nouns). Women talk more than men.
With some nouns after at / to / from. She's not at home today.
Before meals, days and months. I never have breakfast on Sundays.
Before next / last + days, week, etc. See you next Friday.

Blur - Parklife

Quantifiers

Large quantities
Use a lot of / lots of in (+) sentences
They have a lot of books.
She has lots of friends.
Use a lot when there is no noun. He studies a lot.
Much / many are normally used  in (-) sentences and (?), but a lot of can also be used.
There aren't many cafés near here.
Do you watch much TV?
Use plenty of in (+) sentences to mean as much as we need or more.
Don't run. We have plenty of time.

Small quantities
Use little + uncountable nouns, few + plural countable nouns.
Do you want some ice cream? Just a little.
The town only has a few cinemas.
A little and a few = some, but not a lot,
Very little and very few = not much / many.
Hurry up. We have very little time.
I have very few close friends.

Zero quantity
Use any for zero quantity with a (-) verb. Use no with a (+) verb.
There isn't any room in the car.
There's no room in the car.
Use none (without a noun) in short answers.
How much money do you have? None.

More than you need or want / less than you need
Use too + adjective, too much + uncountable nou, too many + plural countable nouns.
There's too much traffic.
Use enough before a noun but after an adjective.
There aren't enough pubs.

Usually and Use to

Present habits and states.
I usually get up at 8.00 on school days.
Past habits and states.
I used to go out with that girl when I was at school.

For present habits use usually or normally + present simple.
For past habits use used to / didn't use to + infinitive. Used to doesn't exist in the present tense.
We use used to for things that were true over a period of time in the past. It usually refers to something which is not true now.
Used to / didn't use to can be used with actions verbs (wear, go, ...) and non-action verbs (be, have, ...)
We often use not ... any more / any longer with the present simple to contrast with used to. I used to go to the gym but I don't any more/any longer.

Second conditional

Second conditional sentences: if + past simple, would/wouldn't + infinitive
Use the second conditional to talk about a hypotetical/imaginary situation in the present or future and its consequence.
Compare:
Real situation: I don't have much money, so I can't buy a bigger house.
Hypotetical situation: If I had money, I'd buy a bigger house.
Use the second conditionals beginning If I were you, I'd ... to give advice. Here you can't use If I was you.

Would / wouldn't + infinitive
You can also use would / wouldn't + infinitive (without an if clause) when you talk about imaginary situations.
My ideal holiday would be a week in the Bahamas.
The contraction of would is 'd.

!!!!!!
Remember the difference between first and second conditional:
If I have time, I'll help you. A possible situation. I may have time.
If I had time, I'd help you. An imaginary/hypotetical situation. I don't / won't have time.

First conditional and future time clauses + when, until, etc.

First conditional sentences: if (or unless) + present simple, will/won't + infinitive

Use the present tense (Not the future) after if in first conditional tenses. If you don't do more work, you'll fail the exam.

Unless = If ... not. I won't go unless she invites me. I won't go if she doesn't invite me.

You can also use an imperative instead of the will clause. Come and see us next week if you have time.

Future time clauses

Use the present simple (Not the future) after when, as soon as, until, before and after to talk about the future.

I'll call you as soon as I arrive.

We'll have dinner when your father gets home.

I won't go to bed until you come home.

I'll have lunch before I leae.

After I finish university, I'll probably take a year off and travel.

Can, could, be able to (ability and possibility) II

Más información y ejercicios sobre estos modal verbs:

http://www.englishclub.com/grammar/verbs-modals_can.htm

http://elblogdelingles.blogspot.com/2006/05/lesson-17-can-could-and-be-able-to.html

http://www.autoenglish.org/gr.can.i.htm

Can, could, be able to (ability and possibility)

Can / Could
I can speak Spanish very well.
She could play the violin when she was three.
Could you open that door, please?
Can is a modal verb. It only has a present, past, and conditional form (but can also be used with a future meaning).
For other tenses and forms use be able to.

Be able to + Infinitive
I am able to accept your invitation.
They weren't able to come.
I'll be able to practise my English in London.
I'd like to be able to ski.
You can use be able to in the present, past, future, present perfect, and as a gerund or infinitive.
Be able to in the present and past is more formal than can/could.

Must, may, might, can't (deduction)

When you are sure something is true: must
They must be out. There aren't any light on.

When you think something is possibly true: may/might
His phone's switched off. He might be on the plane now.
He hasn't written. He may not have my address.

When you are sure something is impossible / not true: can't
He can't be ill. I saw him at the gym.
They can't be Italian. They're speaking to each other in English.

We often use must, may/might, and can't to say how sure or certain we are about something (based on the information we have).
In this context, the opposite of must is can't, not musn't.

Must, have to, should (obligation)

obligation / necessity: have to / must (infinitive)
Must and have to have a very similar meaning.
Have to is more common for general, external obligations, for example rules and laws.
Must is more common for specific or personal obligations.
Compare: I have to wear a shirt and tie at work (It's the rule in this company). I must buy a new shirt - this one is too old now (It's my own decision).
Have to is a normal verb and it exists in all tenses.
Must is a modal verb. The only forms are must and mustn't.
You can also use have to or must for strong recommendations. You have to/must see that film. It's fantastic.

no obligation / necessity: don't have to. ---- prohibition: mustn't (+ infinitive)
Don't have to and mustn't are completely different.
Compare: You mustn't drive along this street (It's prohibited, against the law). You don't have to drive - We can get a train (You can drive if you want to but it's not necessary/obligatory).
You can often use can't or not allowed to instead of mustn't.

advice or opinion: should/shouldn't (+infinitive)
Should is not as strong as must/have to. We use it to say if we think something is the right or wrong thing to do.
Should is a modal verb. The only form are should or shouldn't.
You can also use ought to and ought not to instead of should/shouldn't.

Comparatives and superlatives

Comparing two things (or actions)
Regular comparatives adjectives/adverbs:
hard/harder, big/bigger, easy/easier, modern/more modern,
Irregular comparative adjectives/adverbs:
good-well/better, bad-badly/worse, far/furhter
After than or as we can use an object pronoun me, him, her, etc. or a subject pronoun (I, he, she) + auxiliary verb: She's taller than me or She's taller than I am.

Superlatives
Form superlatives like comparatives but use -est or most/least(lo más mínimo).
You normally use the before superlative, but you can also use possessive adjectives: Their most famous song.

What are you sinking about?! - Communication problems

Improve your English!

Present perfect continuous

Present continuous for unfinished actions
Have/Has been + Verb+ing
Use the present perfect continuous with for and since with action verbs.
How long have you been learning Spanish?
He's been studying here since September.
They've been going out together for four years.

!!!!!
With non-action verbs (know, be, etc.) use the present perfect simple, NOT the present perfect continuous. with for and since. I've known her for ages. NOT I've been knowing her for ages.
With live and work you can use the present perfect simple or continuous with for and since. I've been living here for six months. I've lived here for six months.

Present perfect continuous for recent continuous actions
Use the present perfect continuous for actions which have been going on very recently. They have usually just stopped.
Your eyes are red. Have you been crying? No, I've been cutting onion.

Flight of the Conchords - Business Time

Present perfect and past simple

Present perfect: have/has + past participle (studied, been, ...)
Past experiences.
I've been to London, but I haven't been to Paris.
She's never met his ex-wife.
Have you ever lost your mobile?
We often use ever and never when we ask or talk about past experiences. They go BEFORE the main verb.
Recent past actions.
He's just arrived at the room.
With yet and already (for emphasis)
I've already done my homework. 
Have you finished yet?
My brother hasn't found a new job yet.
Just and already go BEFORE the main verb in positive sentences, yet goes AT THE END of the phrase in negative sentences and questions.
Unfinished states (non-action verbs) which start in the past and are still true now.
They've known each other for 10 years.
How long have they been married? Since 2003.
Use How long...? + present perfect to ask about an unfinished period of time (from the past until now).
Use for+a period of time, or since with a point of time.

Present perfect or past simple?
Use the present perfect when there is a connection between the past and the present.
Use the past simple to ask or talk about finished actions in the past, when the time is mentioned or understood. We often use a past time expression.
I've been to Barcelona twice.(= in my life up to now) I went there in 1997 and 2009. (= on two specific occasions)
How long have you been married to Jane? (= you are married to Jane now) How long were you married to Jane? (= you are not married to Jane now)
I've bought a new computer. (= I don't say exactly when) I bought it on Friday. (= I say when)

Future forms

Be going to + infinitive
Use going to, NOT will/won't, when you have already decided to do something.
Future plans and intentions
My brother's going to adopt a child.
I'm not going to go to Barcelona next week.
Predictions
It's going to rain.
With the verb go you can leave out the infinitive. I'm going (to go) to New York.

Present continuous: be + verb + ing
You can usually use present continuous or going to for future plans/arragements.
Going to shows that you have made a decision. We're going to get married in the summer.
Present continuous emphasizes that you have made the arrangements. We're getting married on July 12th.
Future arrangements
They're meeting at 10:00.
She's leaving on Friday.

Will/shall + infinitive
Use will/won't for:
Instant decisions. I'll have the steak.
Promises. I won't tell anybody where you are.
Offers. I'll carry that bag for you. Shall I help you with your homework.
Suggestions. Shall we eat out tonight?
Use shall with I and We for offers and suggestions when they are in questions.
Use will or going to for predictions.