You will need
  • computer;
  • - graphic editor;
  • skills freehand drawing.
In the graphics editor, create a new document with a size of 300x300. Set the resolution to 72 dpi. If there is such option in the basic settings adjust the image interpolation "to neighboring pixels" that the picture had sharp edges, not smoothed.
Imagine the process of creating your drawing, just like putting some image of bricks, the value of which is only 1 pixel (the basic unit of the raster image). In this case, all elements of the composition should be commensurate with this value. Lines wider than 1 pixel permissible only in extreme cases.
Draw with Pencil tool, size 1 pixel, to remove lines and pixels, use the Eraser of the same size. When you look at the picture the viewer should clearly see a pixelated pattern with its distinctive lines, consisting of uniformly offset by 1 pixel lines to form the "step". However, the strong "serrations" spoils the appearance of the graphics, so all the uneven curves or sharp bends in lines should be carefully corrected, to make more smooth and fluid.
To mix colors, create smooth transitions between them and to give volume to the elements of the picture, use the technique of "dither", i.e. "mixing". This technique consists in the arrangement of pixels of two adjacent colors in a checkerboard pattern at a certain interval between these colors. To make a mixing zone less than two pixels are not necessary, because the smoothing of the monitor screen will destroy the effect. "Dither" also allows you to get colors that are not in the palette of the graphical editor.
To simplify the drawing process may create a preliminary sketch or pencil on paper (and subsequent scan), or by using a tablet directly in your graphic editor. Then bring the sketch to mind, using the principles and techniques of pixel art, as described above.
Overall, the main skill you should be the ability to add or remove pixels to create crisp lines and shapes, not lost and not lubricated in the thumbnail. You can learn it, just practicing, studying and copying the works of recognized masters and creating your own drawings.