Sewing a button seems like a simple task, but if you're not careful, sewing it on without spacing it properly will make your clothes tight and the button difficult to open and close. Make sure your buttons always sit correctly by using a toothpick to add the right amount of thread slack.
Next time you're sewing a button onto a jacket or shirt, place the toothpick in the middle of the button. Then, sew between the holes on either side of the toothpick so that the thread loops over the toothpick. When you're done, slide the toothpick out from under the thread and gently pull the button forward.
Now the thread that was being held in place by the toothpick is behind the button. This gives you just the right amount of slack in the thread. Your buttons should sit perfectly, and your clothes should fit nicely too.
The Best Way to Sew on a Button [Apartment Therapy]