Check to make sure flat surfaces are truly flat. Take a piece of 400-grit sandpaper, place it flat on your work surface, and sand both sides of your piece. If the sanding pattern is uneven, where there are spots that are not sanded, then it isn’t flat. Cutting and sawing metal can cause some warping. Use a leather or nylon mallet to lightly tap the metal back to flat.
Bevel your edges to give your work a professional, finished look. This one detail can make a big difference in how you piece looks. You can do this by angling a file when you file the edge to bevel it, or using a wheel on a flex shaft or Dremel. After you have beveled the edges, go back over the edge to make sure it is smooth from the beveling.
Get smooth curves. Anneal the metal before shaping and rounding. This will allow the metal to move easily without any kinking from work harden areas. When shaping move the metal in stages rather than trying to get all the shaping in the first bend of the metal. If the metal begins to resist, anneal again to make it easier to shape.