Elizabeth Warren uses cold-calling in the classroom, too!

​An important technique of my classrooms has been cold-calling, using random selection of students. 

Here's a progressive politics rationale for that!

https://chroniclevitae.com/news/2244-what-elizabeth-warren-can-teach-us-about-teaching

Actually, they don't fully describe her classroom process, as it sounds like she's only  random with a subset.  But the general idea is there!

At least she's not simply calling on those with their hands raised--that's patently unfair, in my book.

What methods have I used? 

The best I've found, for K-12 students anyway, is the popsicle stick method, with a can that contains one stick with each student's name on it.  I publicly display the can, ask a question, then publicly select a stick.  Everyone pays attention.  Nobody's left out.  (I admit to occasionally cheating, in unusual cases, to avoid calling on someone.  But even then, I go through the motions so that the process seems fair.)  

I have also built an excel spreadsheet that selects a random name from a given list; or builds a randomly-sorted list of names.   The latter works well for assigning, say, parts in a play, or group work.  But the computer seems too artificial and slow to use during a (necessarily) fast-paced classroom discussion. 

I have also used an iPhone app that displays a random name from among a given list -- again, that's artificial and not as patently obvious as the sticks.  Unless it's actually mirroring an onscreen display, the answer is not patently obvious to the students.

I have also, when lacking any of the above tools, simply tried my own obviously-human random selection, sometimes by patently waving my hand above a list and pointing at a name.  This reassures us all that my point is to randomly select someone -- students like the "fairness" of that.  Or at least they cannot complain, because it is more "fair" than the traditional teacher method of calling on hand-raisers or purposely calling on perceived slackers.  

The randomness is important from both the student and the teacher point of view -- it keeps us both on our toes.  I need to be sure that my question is reasonably answerable, given what I have covered in class.  Again, I confess that in a weak moment I have called on The Student Who Is Sure To Have The Answer That I Want;  or the student who is dozing.  But in general I try to follow random selection for cold-calling.