FORM
[am/is/are + present participle]
Examples:
* You are watching TV.
* Are you watching TV?
* You are not watching TV.
USE 1 Now

Use the Present Continuous with Normal Verbs to express the idea that something is happening now, at this very moment. It can also be used to show that something is not happening now.
Examples:
* You are learning English now.
* You are not swimming now.
* Are you sleeping?
* I am sitting.
* I am not standing.
* Is he sitting or standing?
* They are reading their books.
* They are not watching television.
* What are you doing?
* Why aren't you doing your homework?
USE 2 Longer Actions in Progress Now

In English, "now" can mean: this second, today, this month, this year, this century, and so on. Sometimes, we use the Present Continuous to say that we are in the process of doing a longer action which is in progress; however, we might not be doing it at this exact second.
Examples: (All of these sentences can be said while eating dinner in a restaurant.)
* I am studying to become a doctor.
* I am not studying to become a dentist.
* I am reading the book Tom Sawyer.
* I am not reading any books right now.
* Are you working on any special projects at work?
* Aren't you teaching at the university now?
USE 3 Near Future

Sometimes, speakers use the Present Continuous to indicate that something will or will not happen in the near future.
Examples:
* I am meeting some friends after work.
* I am not going to the party tonight.
* Is he visiting his parents next weekend?
* Isn't he coming with us tonight?
USE 4 Repetition and Irritation with "Always"

The Present Continuous with words such as "always" or "constantly" expresses the idea that something irritating or shocking often happens. Notice that the meaning is like Simple Present, but with negative emotion. Remember to put the words "always" or "constantly" between "be" and "verb+ing."
Examples:
* She is always coming to class late.
* He is constantly talking. I wish he would shut up.
* I don't like them because they are always complaining.
REMEMBER Non-Continuous Verbs/ Mixed Verbs
It is important to remember that Non-Continuous Verbs cannot be used in any continuous tenses. Also, certain non-continuous meanings for Mixed Verbs cannot be used in continuous tenses. Instead of using Present Continuous with these verbs, you must use Simple Present.
Examples:
* She is loving this chocolate ice cream. Not Correct
* She loves this chocolate ice cream. Correct
ADVERB PLACEMENT
The examples below show the placement for grammar adverbs such as: always, only, never, ever, still, just, etc.
Examples:
* You are still watching TV.
* Are you still watching TV?
ACTIVE / PASSIVE
Examples:
* Right now, Tom is writing the letter. Active
* Right now, the letter is being written by Tom. Passive
BE CAREFUL! Some verbs are not used in the continuous form - see below.
Verbs that are not normally used in the continuous form
The verbs in the list below are normally used in the simple form, because they refer to states, rather than actions or processes:
List of common verbs normally used in simple form:
Senses / Perception
feel*, hear, see*, smell, taste
Opinion
assume, believe, consider, doubt, feel (= think), find (= consider), suppose, think*
Mental states
forget, imagine, know, mean, notice, recognise, remember, understand
Emotions / desires
envy, fear, dislike, hate, hope, like, love, mind, prefer, regret, want, wish
Measurement
contain, cost, hold, measure, weigh
Others
look (=resemble), seem, be (in most cases), have (when it means to possess)*
Notes:
1. 'Perception' verbs (see, hear, feel, taste, smell) are often used with 'can': e.g. I can see...
2. * These verbs may be used in the continuous form but with a different meaning, compare:
a. This coat feels nice and warm. (= your perception of the coat's qualities)
b. John's feeling much better now (= his health is improving)
a. She has three dogs and a cat. (=possession)
b. She's having supper. (= She's eating)
a. I can see Anthony in the garden (= perception)
b. I'm seeing Anthony later (= We are planning to meet)
Examples:
* I wish I was in Greece now.
* She wants to see him now.
* I don't understand why he is shouting.
* I feel we are making a mistake.
* This glass holds half a litre.