Essential Tools #2: Clips!
/I don't know what these are technically called, but boy are they handy! They also fall into the category of "I didn't know I needed them until I had them."
When what you're sewing is too thick for pins, use clips! I use them often in bag-making because of the heavy fabrics and multiple layers. In this picture I'm sewing the zipper ends onto the zippers. What's a zipper end?? See the finished product below. You can make a pouch with the zipper ending in the side seams, but zipper ends give a more finished and structured look. And they are not difficult to make. Often it's the little touches that make handmade special.