1. First of all make a new file in Photoshop, I used a size of 210x360.
2. In the new document draw about 20-40 squares and fill them with random colours. (Try get as many colour variations in as possible.)
My squares were each 40x40 pixels in size.
3. In the layers window add a solid color layer by clicking create new fill or adjustment layer button and choosing Solid Color from the drop down menu.
4. Lower the opacity for the color layer to 80%, then change the layer mode to Color.
Since I used a pinkish color I'm left with this palette:
Now you have a very good colour palette you can use in your design that will work well together.
Save colour palette images as gif files and open them up any time you need a good palette.
More Tutorials: 
