Painting From A Reference

I have my idea for a new painting, now how do I get started? I can use reference images, photos I have taken or found. I could make something up from my imagination and or memory, or I could look at something right in front of me, maybe a still life or a scene somewhere. My choice, my freedom. I have tried all of these approaches and they are all valid and each has their own challenges. I am going to rank them , in my opinion, from easiest to least easy. 
OK this is all just my subjective opinion but I think the easiest way to start a painting is with a photo that is ready to go. The composition is already there, the subject matter has everything needed, so I only have to copy it. It is best if I took the photo. The reason I think this is the easiest is because it is already a two dimensional image and I am transcribing it to another 2D image. Also it doesn't need editing, that is taking out or adding other elements to the scene. 
The more common example and next in my hierarchy is to use a reference photo but make changes to it. It could be adding or removing elements, maybe combining parts of more than one photo. It could also be changing the colors. In other words it is not a copy of the photo but the photo is used for inspiration. 
The next way of working is to use real life for the reference instead of a photo. Within that category looking at something in a controlled environment, such as a still life set up, or a model is easier than being outdoors where the light is always changing, such as en plein air.  
​The most difficult way of making a painting, for me, is without any reference. Of course that is assuming I am attempting realism, abstract painting is a whole other topic. Painting without any reference requires using only my memory and imagination. It is the ultimate in creativity. The more I paint something the easier it gets to paint it without reference. The painting below was painted from imagination.