What's the best way to go about painting a mural on a white wall?

Pinterest has lots of ideas:

https://www.pinterest.com/explore/painted-wall-murals/?lp=true

This person had a cool idea:

http://www.techeblog.com/index.php/tech-gadget/how-one-geek-created-an-amazing-wall-mural-with-no-drawing-skills-just-technology

Based on my limited experience. Don't

First wash the wall with TSP so you have a clean surface to work with. If you have a background color, now is the time to paint that. Draw or stencil on your mural on the wall in pencil or chalk. Then paint!

Depends on how good an artist you are . Some can free hand like my husband and step sons, they are all amazing ! Some people (me) need to transfer or trace patterns with a pencil first and paint over them . No shame in using homemade stencils or tracing if you need to ! Have fun with it . Art is subjective.

this is a room in an inn in Portland Maine. I knew the artist who painted this complete wall mural (and many others) she said she just started in one corner and continued! My husband is an artist and he painted a long mural on an outdoor fence. He just used a photograph for reference and drew it on, then painted. If I a much lesser talent were to do it I would use graph paper and figure out where my elements would go.

First, you need an idea of what you want. You then should draw that scene on your wall. A projector is fantastic for this. Then I would use acrylic paints use an extender to give you more "play" time for blending and highlighting/shading where needed. always make sure you have a reference point to home in on so you are always lined up in case you have to take extended breaks from it which I'm sure you will. Or, you can just go at it willy nilly graffiti style/ free hand style.

Have you thought of using a projector to project your picture on the wall and then just kind of trace the parts you want?

There are actually murals you can buy that are like stencils. I found they work very well.