Sewing Rules: Darts are always folded from the fabric's wrong side following dart lines transferred from pattern to fabric.
An important step in the dart sewing process, is transferring the marks form the paper patterns to the corresponding fabric pieces such that they are marked on the fabric's wrong side. Naturally, the finished dart intake should correspond to the wrong side of the garment, thus transferring all marking to the fabric wrong side will not only protect the fabric's face side form staining, it will also provide a way to easily fold the intake as needed in the dressmaking process. The center fold line provide an accurate folding guideline while the two dart lines on each side provide an exact stitching line.
On the right side of the garment, the finished dart seam should lay smooth and flat with all intake ironed flat and enclosed on the wrong side of the garment.