Tips and Tricks to Sew Corners

Problems with corners usually happen because of the seam allowance that is filling up the corner. Trimming, clipping and notching are all ways to control the seam allowance. Controlling the seam allowance allows for nicely laying smooth seams.
Notching and clipping on inner and outer curved seams controls the way the seam allowance over laps and lays inside the item. Notching removes pieces of the seam allowance to prevent it doubling up, laying on itself, creating unwanted bulk. Clipping allows the seam allowance to spread and lay smoothly.
Loosely woven fabric may require you to stagger the clipping and notching so that the seam is not weakened in one spot. Simply notch or clip one layer at a time and move over so that the layers of the seam allowance are not treated in the exact same spot.
Clipping and notching in conjunction with grading the seam will help eliminate the abruptness of the seam allowance edge inside the garment. How to Grade a Seam