Well...here's how i do
First i scan the drawing in high resolution (something like 3500px x 1800px),then fix exposure,cleaning some lines.
After this,hands to the phone
here it comes the colouring phase : sometimes i leave the resolution untouched....but if i need,i resize the whole pic in the size i usually upload here.
After colouring,shading,and add some effects i check if i coloured correctly and then crop the borders...
After all of this,i upload the pic