If you or the HRT you teach with likes to line students up in two lines and have them rotate so they can practice a certain dialog point with many different partners, this explains how to do it right.
The Normal Way
The normal way to do line conversations is to make two lines of students facing each other. They complete the action then everyone rotates one position, let's say, anti-clockise.
I've used tables to illustrate. Imagine S1 is student 1 and they are lined up in two lines horizontally.
In the scenario below, the first student (S1) would be talking with S6, S2 with S5 and so on. They rotate and the new positions would be as seen in iteration 2.
In the first iteration, S1 talks with S6. In the second iteration, S1 talks with S2.
In the third iteration, S1 talks to S4. In the 4th iteration, when there are still students S1 hasn't spoken with, she is back to speaking with S6.
In this scenario, S1 will never speak to S3 or S5.
Because both lines of students are moving, effectively in opposite directions, each student always skips every other student. With an even number of students, no matter how many rotations there are, roughly half the class will never match up.
What We Want
Basically, we want each student to have the chance to speak with every other student. Why? Because repitition is boring enough without doubling up on it!
In a class of 34 students, there should be an opportunity for students to speak with 33 others. The normal way, described above, attempts to do this but is inefficicent and after speaking to half the class, each student gets put opposite their first partner again. The other half of the class is skipped with every rotation.
The solution is easiest to implement when there are an odd number of students because you will join the short line and become the solution. You solve the inefficiency problem by not moving. In the case there are an even nnumber of students, simply ask one student to never move and the other students rotate around her.
In this scenario, there are an odd number of students and you have joined the short row. If there are an even number, simply allocate your position to a students. Your role is the stationary teacher (ST) while all students rotate.
In iteration 1, S1 speaks with ST. In iteration 2, S1 speaks with S3.
S1 then proceeds to speak with S5, S2, and finally S4. She has now spoken to every other student in the class.
The solution lies in making each student take a turn stepping out of the rotation. They do that when they speak with the stationary teacher (or student).
Even though these lined up speaking drills aren't the most exciting, sometimes they come up. Hopefully, this helps you get better efficiency out of your lined up conversation practice time. But seriously, avoid this kind of repetitive drilling whenever possible.