Do not rush to grab a can and run to the nearest wall, you first need to draw the sketch or the sketch. To draw it better with a pencil and only when you fully love, you can trace it with a marker and fill color. And even if the sketch is ready, think before you run outside. Up to this point may take a few months and painted dozens, maybe hundreds of thumbnails.
And yet, if you decide to transfer your sketch on the wall. Begin with a sketch with the same color as the background sheet. Then apply the background and draw the outline. Such a sequence is convenient, as any mistake can be corrected. If the paint drips, don't try to stop her, better to wait until the paint dries and the paint flowed over. In order to avoid stains, all lines must be done carefully, without jerking, but at the same time quickly. All lines should be smooth without breaks.
Professional writers under each picture put your "tag", i.e. a personal signature. It is usually up in advance and decorated with question marks and exclamation points and other "chips". It is important that the tag was written quickly and look stylish. Writers usually draw it by special markers, not paint. Once it is set, drawing is completed.