Here are three tutorials that offer tips and tricks to help you successfully sew elastic waistbands.
Stretch Fabric Waistbands — Christine Jonson Sewing Patterns
Tribal Print Cashmere Feel Unisex Scarf With Fringe –
How to sew the perfect waistband – By Hand London
Top Down Center Out with the Eve Trousers – The Crooked Hem
Attach elastic to a waistband – no casing or twisting! - Cucicucicoo
How to Sew an Elastic Waist Dress
Sewing an Elastic Waistband - Threads
A New Trick for Waistband Elastic – The Sewful Life
How to Sew Elastic, Easily for Beginners
Tutorial/Video: Sewing elastic into waist tunnel casing in ONE step! - Sew Tessuti Blog
How to Sew an Easy Elastic-Waist Gathered Skirt
How to Sew and Topstitch an Elastic Waistband » Helen's Closet Patterns
Sewing Glossary: Three Ways To Sew Elastic Waistband Tutorial – the thread