sorry in advance for the formatting,
This was how I was taught.
arg(z-z0) - arg(z-z1) = θ
is a locus that can either be a major arc, minor arc, straight line or a semi-circle. This all depends on the angle θ.
an angle between 0 and π/2 would be a major arc, an angle of π/2 would be a semi-circle, an angle between π/2 and π would be a minor arc while an angle of π would be a straight line from one point to another, excluding those points. This would all be drawn in an anti-clockwise direction starting from z0 and ending at z1.
So basically, you end up with a semi-circle with its middle cut off from point (2,0) to point (-2,0) and an internal angle of π.
I remembered these by heart so when I got into the exam I was confident enough to draw these instead of solving algebraically. I have a sheet of notes on all of the possible questions that I can find if you need me to.