I think it's worth mentioning some of the complexities involved, though many of these were mentioned at the thread Andrew links to.
Choice of tense probably isn't as clear-cut as we'd like to think. For instance, with disease-related examples as mentioned in the link:
I have diabetes /a cold / occasional headaches / frequent headaches.
*I am having diabetes / a cold.
I am having occasional headaches / frequent headaches.
The use of have as a near-synonym of get / take (punctual) as well as possess / suffer from (durative) is doubtless a complicating factor here.
Turning to the multi-word verb get on, we see that again there is idiosyncratic behaviour dependent upon the particular 'object referent' (whether stated overtly or not):
I hear you've got a new job. How are you getting on? [ie with your new job]
I was sorry to hear that you and Bill had a big argument (last month). How are you
getting on with him now?
I was sorry to hear that you and Bill had a big argument. How are you
getting on now?
and for the do + bare infinitive:
*I hear you've got a new job. How do you get on?
Travelling by bus must be hard for you now. How do you get on? [different sense of get on, of course]
*I was sorry to hear that you and Bill had a big argument last week. How do you
get on (with him) now?
I was sorry to hear that you and Bill had a big argument last year. How do you
get on (with him) now?
There seem to be subtleties involving not only the continuous / repetitive distinction, but also whether the present state can be regarded as steady (involving how long it has continued).