You shouldn't see vaguely. You should memorize the concrete status of the students.

3. Moving around the classroom
... Continued from the previous blog.

4) You shouldn't go easily to the students who call you.

What kind of things the students write? what meaning the things they wrote have? you should train yourself to grab these things at the glance and memorize them.
Using this kind of information, you can make a student stand up, or make them say something, or make them write on the board, or you can make the strategy of the order of student's speech.
That is all I said the very first steps of moving around the classroom.