What do I do to a door knob to open the door?

Solution 1:

What you do to the doorknob is turn it.

Please press the button before turning the doorknob.

And just to demonstrate that this is a verb (or in fact the verb) that people actually use, here are the top 20 collocations from the Corpus of Contemporary American English (COCA):

 turned the doorknob    19  
 tried the doorknob     17  
 twisted the doorknob   11  
 touched the doorknob    8  
 grabs the doorknob      7  
 turn the doorknob       7  
 turning the doorknob    6  
 tries the doorknob      6  
 rattling the doorknob   4  
 rattles the doorknob    4  
 turns the doorknob      3  
 see the doorknob        3  
 rattled the doorknob    3  
 grasped the doorknob    3  
 find the doorknob       2  
 found the doorknob      2  
 jiggling the doorknob   2  
 jiggles the doorknob    2  
 grips the doorknob      2  
 gripping the doorknob   2

As you can see, out of the many things people like to do to doorknobs in various situations, only turn and twist really fit the bill in yours, "the action of rotating or moving or twisting a doorknob". And while your very own twist is quite high on the list in its simple-past form, it is outnumbered by the corresponding form of turn, and other forms of turn are breathing down its neck with no corresponding forms of twist in sight.

Lastly, just to round it up before I'm accused of being US-centric, here are the stats from the British National Corpus as well:

turn the doorknob        2
tried the doorknob       1
feel the doorknob        1
describing the doorknob  1

That's not statistically significant in and of itself (due to the smaller corpus size), but it does nicely complement the COCA results.