Setting scale and adjusting references, and first modeling
Okay, we have taken the time to get clear, cropped reference photos, and imported them into blender using orthographic mode and setting the correct orientation using the (CTRL+)1/3/7/9 on the number pad.
Now, we must set the scale in blender and adjust the reference photos to represent the real world.
Setting Scale in Blender to mm
Here we set the dimensions of the cube to the 3 dimensions we took with a caliper of the shift knob. (This step must be precise). We then scale/move each image (using num pad and ortho. view) to fit nicely into the cube. Take your time here!
If the above step is an issue, you may need to change the opacity of the images. The cube may also be moved only on one axis, but should be zeroed to the origin again for each view.
We then create a plane, delete two vertices, and position accurately in front/back/side views. Then we use Extrude (E) in orthographic side view to the shape of the shift knob. Use front and back views to see where to start and stop.
(NOTE: this image was taken after many iterations, the first version was perfectly aligned to the image and was a slight bit off. The far left vertices are a loop cut which was Scaled (S) to ad a curve to the shape.)