"Murals" sounds so fancy. Personally, I just paint on my walls because it makes me happy. A dab here, a dab there...I draw a picture I want to look at for a while.
I thought I'd share a bit of my process.
1. Find inspiration and keep it simple. Probably my best mural was at our old house, and it was based on a children's book with simple colors.
2. Gather some acrylic house paint, preferably flat or clearance, you want to use. In a pinch I've used craft paint or artist paint to adjust a color or make just a small amount.
Using leftover plastic food tubs, I mix the colors I plan to use. This is the same process I use with a landscape painting. Keep it to 4 or 5 colors, and make sure they look good together keeping in mind hue, shade, values, etc. If you don't know what those words mean - just stick to your inspiration piece colors.
3. Prime the surface if necessary. Then take vine charcoal and lay out a rough outline. Lay in your big blocks of color - doing all the browns, then blues, etc. I always love to start with the sky. I love skies. You can see this process clearly in the middle mural, which is only half done. It's been that way for awhile, but I enjoy it just as it is. Come back in, usually on another day, with a different color or another layer. Don't overdo the project, just enjoy.
One son wanted a rainbow by his bed - so he has one. His bed was too messy to take a picture of the rainbow. We have a few palm trees in our upstairs bathroom - just cause it reminded me of Curious George Gets a Job.
4. When you are relatively happy sign your name and date it in a corner - I'm so glad I did this so now I know when I did each mural. It's ok to make changes, etc.
I know some people worry about ruining the walls, but really, you can paint over it if you don't like it. Especially if you use a "dry brush" technique. That means your brush is not loaded with paint that dries with little ridges - a dry brush shows the brush marks (see Under the Sea).
Mostly have fun...they are just walls. The only murals I don't like are the ones where the painter is stiff and timid. Where it looks like it was painful. If your mural "primitive" or "organic" that's ok, no one said you have to create a Michaelangelo.
Last secret - go BIG - cover all four walls with something simple. It makes a big impression.
Let me know if I've inspired you, I'd be glad to share my experiences with anyone wanting to try a mural themselves.