When I hung my siding, I cut a short piece of starter strip, about a foot long and a 6" piece of siding to use as a template. Then I went around the building with this template and marked the lowest starter strip height, on the building at several locations, that would let the siding snap in. Then with a rotary laser level, marked a level line around the building. Finally, measured down to the starter strip marks and found the highest one, which was used to establish a level starter strip line around the building.
I looked for a photo that showed the lines but couldn't find one.
Good luck with your install.