Six Tips for Sewing a Button Like a Pro
Before you start sewing
Match replacement button to weight of fabric
If you can't find a button that matches the original set, make sure your replacement buttons matches the weight of the fabric. If your button is too heavy it will pull the fabric out of shape, or might even tear it. If your button is too light, it might not hold your garment closed.
Test replacement button through buttonhole
Make sure your replacement button fits snugly but easily through the buttonhole. Mark where the button should be attached with a pin.
Match thread to original
Mismatched thread is an obvious sign that the garment has been mended. If you don't mind a quirky visible mend, that's fine. But if you want your replacement button to look like its always been there, get a good colour match to the thread on the original buttons.
Use a doubled thread
Thread your needle with a piece of thread about as long as your forearm. Make the tails the same length.
As you sew
Avoid loops and twists
Check for loops and twists as you sew and pull the thread taut and straight at every stitch.
Make tiny, tidy knots
Tie a neat knot in the ends of your doubled thread and snip the excess before you start to sew. When you the button is firmly attached, make 3 small firm stitches on top of each other at the back of the garment to finish it off.
Let me know in the comments if you have any more button sewing tips to share.