Get to know your sewing machine.
I had a client in for a one-to-one tutorial this week who was having trouble altering her T-shirts. She was quite short in the body and needed to take up most of her tops or they were more like mini-dresses. She’d bought a new sewing machine last year, and came to me for help convinced that the tension was wrong. The top she had recently altered had several breaks in the sewing of the hem and there were lots of skipped stitches.