Mic positioning in 2 sitting actors scene
It is more important for the mic to be close enough to the talent than it is for the mic to be pointed perfectly on-axis at the talent's mouth.  A cardiod 12" away that's 45 degrees off-axis will likely sound better than a cardiod 36" away that's dead-on.  Shotgun mics give you a bit more range, and a bit less tolerance for off-axis pickup.  But then again, the table may provide a very good early reflection that reinforces the actors voice and allows you to simply mic straight down with good results.

Depending on the size of the table, and where the actors' projection lines converge, you might be able to get away with a single mic aimed down between them, or you might effectively need two mics (either physically or by shuttling a single mic between them as they trade lines).

The key to successful sound recording is to know the principles of mic patterns and behaviors so that you can properly prepare for a session and successfully understand why you might be hearing what you hear when you actually put up the mics.  But that is only the starting point.  You must then always always always use your ears to adjust from what the principles predict to what actually works in the specific case with which you are dealing.