Question

I do not know when I should -ing form. By example: I want to know..., or I want knowing...?

Answer 1

-ing is usually used as a verb, something that is happening right now.  For example, "I am driving to the store" or "I am talking to you."  Sometimes it is used as an adjective to describe a noun like, "Drink from the running water" or "Speak to that working man."  In your example, it would be either "I want to know." or "I want a working knowledge."

Answer 2

Thanks, Aegelis. But what happen when -ing is a noun? I confess you this issue is confusing for me.

Thanks again,

Guido 

Answer 3

I see. I suppose there's no change, like in these sentences:

1.    Seeing is believing.
2.    Reading that book was very interesting.
3.    Drinking is essential
4.    Drinking too much pop can make you fat.
5.    Taking the bus was rather a good idea.
6.    Swimming is very good exercise.
7.    Taking too many aspirins is dangerous.
8.    I really like sailing .
9.    This article really needs rewriting.
10.    He drove two hundred miles without ever stopping.
11.    I look forward to seeing  you again next week.
12.    I'm thinking of painting my house.
13.    I started by carefully turning off the electricity
14.    Do you mind shutting the window, please ?
15.    Will you consider taking the job?
16.    I've really enjoyed meeting you.

Source: http://linguapress.com/grammar/gerunds.htm

Answer 4

For describing feelings use verb-ed Ex. I'm bored (I feell bored) For describing a person, or thing as an adjective use verb-ing Ex. I'm boring (because, to talk with me can be bored) Ex. That movie was interesting

Answer 5

After "to" you always use the infinitive form of the verb. No "-ing" after the word "to".

Answer 6

In this specific situation, when you have two verbs, one relating and giving meaning to the other, the first verb has to be conjugated with the subject, and the second always comes in infinitive form (to + verb)  

This usually happens with verbs like "need, want, have, love, hate"

So the first verb you conjugate with the subject and the second comes in infinitive  

I like to eat

I have to go

She wants to stay

We hate to wait

However some of these verbs accept that you use the following verb in -ing form, which will transform the verb into a noun.

These verbs are: like, love, hate and enjoy (verbs of emotion)

Therefore you can say both:

I like to swim - I like swimming