This not a sewing 'technique' per se! but man! this is some seriously clever design! I just loooooooove these fairy wing skirts. This will come in handy when looking for Halloween costume ideas.
Everything you ever wanted to know about bias tapes:
Making your bias tape
Sewing your bias tape
I love it that bias tapes really zazz up any plain looking garment. They can really make or break the final product.