Think of a sine curve. But be careful when you turn. I wouldn't want you to start out at the top and end up at the bottom. It's hard on your camera. In other words, take three photos to capture the width that could actually be done with two.
Panorama software uses the overlap to help blend the two images together.
The more overlap there is, the smoother the transition between images and the more seamless they appear. This would require fewer images with a wider angle lens such as 20mm, and a larger number of images with a narrower angle lens such as 55mm. You should shoot the images vertically, allowing for a taller perspective in the finished product. Use a Tripod Using a tripod makes this whole process much easier. Although it is possible to do without one, I don't recommend it .