The present continuous is used:

-  for an action happening now.

Example:  We are filming the scene now.

-   for  an action happening about this time but not necessarily at the moment of speaking.

Example:  I am reading a play by Shaw.  This may mean ‘at the moment of 

                 speaking’ but may also mean ‘now’ in a more general sense.

-   for a definite arrangement in the near future and it is the most usual way of 

    expressing one’s immediate plans.

Example:  I’m meeting Alex tonight.  He is taking me to the theater.

-   with a point in time to indicate an action which begins before this point and probably

    continues after it.

Example:  At nine I am repeating my script (i.e. I start repeating before nine).

The continuous tenses are normally used for deliberate actions and with verbs of action.  Therefore, non-active verbs can’t be used in the present progressive.

Here is a list of NON-ACTIVE VERBS:

1. State or sense:  be, feel, hear, need, notice, see, seem, smell.

2. Feelings and emotions:  adore, appreciate (=value), desire, detest, fear, hate, like, loathe, love, mind, value, want, wish.

3. mental activity:  agree, appreciate (=understand), believe, expect (=think), feel (=think), feel sure/certain, forget, know, mean, perceive, realize, recall, recognize, recollect, remember, see (=understand), think (=have an opinion), trust (=believe/have confidence in), understand.

4. Possession:  belong, owe, own, possess.

Here are adverbs used with the present progressive and they are placed either at the beginning or end of a sentence.

now,           at the moment,               presently,              for the time being

FORM

The affirmative structure of the present progressive tense is formed by using the present tense of the auxiliary verb to be ( am, are, is) and adding ing to the present participle (the infinitive).

Example:  If you are keeping score, Meryl Streep equals Katharine Hepburn

                 as the most-nominated performer, man or woman, in Oscar history.

Negative structure is formed by putting  NOT after the auxiliary “be” (am, are, is).

Example:  If you are NOT keeping score, you would not know about Oscar

                 history.

The interrogative is formed by inverting subject and auxiliary (be).

Example:  Are you keeping score of the most-nominated performer?