"Wanting" or "want"? (Stative verbs: participial clauses; present continuous usages?)

These sentences are fine, because the -ing form is used as an adjective:

"She reached her hand out, wanting to touch him..."

"Not wanting to talk about it, Clary turned..."

What your English teachers probably meant was that ordinarily we do not use these stative verbs in progressive constructions, like this:

"I am wanting to ask you how ... "
"I am liking this job very much."

But sometimes the 'state' which these verbs designate is conceived as subject to change over time; and when that is the case a progressive construction becomes acceptable. In your last example, for instance, the state is about to come to an end:

"I have been wanting to ask you how ... "

Or in this case, the state has been increasing over time:

I am liking this job more and more every day.

ADD:
Jez objects that ‘native speakers might well say "I am liking this job very much."’ Perhaps so—the progressive construction has been steadily increasing its scope for 300 years now, and it is possible that the punctiliar sense on Facebook has definitively ‘unstatived’ like. But I would not expect to hear this except in a dynamic context as “I’m liking this job now”.

So I would advise Learners not to use the progressive construction. The stative sense is still built in to the word itself, and you can’t sound wrong if you use the simple present; but in some contexts you may sound wrong with the progressive.

My first experience of hearing the "I am wanting to..." form was as a native of NE USA moving to the SE. I saw it as a colloquialism at the time, something like "I am fixing to...", but it does seem to be becoming more common elsewhere, too.

McDonald's ad "i'm loving it" has polluted this conversation. It is not correct to use want, love, need etc in the present progressive forms. McD used the grammar incorrectly so that people would remember the ad. I do say "I've been wanting to ..." and want is not listed on the either static or dynamic verb list. Perhaps it is acceptable now but was not in the past.

I see the "rule" of stative verbs as a general rule saying that in most cases such stative verbs are not used in progressive form. But all the same there may be situations where a progressive form can make sense as in your example 3:

-I've been wanting (all the time) to ask you...

There is a second thing to consider. In English people are so accustomed to using progressives forms that sometimes progressive forms are used of stative verbs for emphasis or whatever. The rule about stative verbs is derived from logic - with some verbs there is no reason to express progress - and from observation of their use. But there is an arbitrary zone where it is difficult to say whether a verb is stative or not. And people don't carry a dictionary around to have a look if the verb they want to use is marked as stative or not. After all a verb has no special feature that let us know that the verb is stative.

I look at this from an old English point of view. I dismiss that time dictates what is proper or not. As in old English, if you were found "wanting" it was used in a negative context, meaning you lacked a skill to do something you attempted. You would not say "I am wanting to learn to ...." whatever. You would say "I want to learn to ....". Yet you could be found wanting if you failed an attempt at something you did not have the skill for. Also for consideration is the premise of saying the most with the least. What takes less to say but conveys the most? "I want ..." or "I am wanting ..."? The use of “want” reduces confusion without using more than is needed to convey the message. Unfortunately as mentioned about the McDonald's ad, we've taught our children via marketing that incorrect use of English is ok. Most people have lost the skill or were never taught to speak English efficiently.

I think as per grammar, we can use 'wanting' as a main verb if we think that its going to be in a progressive form. Such as, I want to the Prime Minister...here I used 'want'but if I am not a prime minister however wish to be in future, I can say ' I am wanting to be the Prime Minister, here am using wanting as a progressive from..which is correct..

We use the verb want to talk about wishes and needs, and to give advice:

What do you want for dinner tonight? (wish or desire)

The kitchen wants painting. (needs)

You want to get your tickets soon before they’re all sold out. (I advise you to)

Most uses of want involve the simple forms of the verb (want, wants, wanted). When we are talking about wishes or desires we can also use the continuous form (is wanting, was wanting, will be wanting).

Source: http://dictionary.cambridge.org/grammar/british-grammar/want

Some examples:

• She reached her hand out, wanting to touch him...

• Not wanting to talk about it, Clary turned...

• Actually, I’ve been wanting to ask you how...

It's pretty simple, actually. The three examples you gave were fine. Note that in the next sentence you said:

I really want to know where I can use it and where I can't.

Notice that you did not say "I am really wanting". Which is good, because the usage of "I am really wanting" is what your English teachers were warning you against.

It really drives me crazy that I don't know it.

Don't worry, you can see that you already know it intuitively.