In this Foundation Concept video Craig looks at the subject of creating sunstars in landscape photographs and discusses the following:

 

- the smallest f-stop on a lens will generally create the strongest effect

 

- using a small portion of the disk of the sun helps too

 

- shooting an additional frame at an overall sharp aperture (aperture is casually used by photographers to mean the same thing as f-stop which is how I am using it here)

 

- combining the frame with the best sunstar with the overall sharp frame to get the best of both worlds - sharpness and contrast where you want it and the sunstar effect