One fun way to get my younger students to stretch at home is to create "Sticker Charts". Print out a calendar and post on the fridge, etc. Each day the student stretches- they put a sticker on their chart. They can bring back their completed chart to class for a prize. Hey- this could work for adults and teens too! :) Keeping yourself motivated is key to sticking to it. And if you forget for a couple days (or weeks)... it's okay! Get back at it and start over.
When should you get started- now! If you're considering auditioning for a competitive team this summer- start stretching daily now. Gains in flexibility is a slow process, it will not happen over night. But it will happen with consistent hard work.
Looking for a way to get started- check out this tutorial video my sister Emily and I made for our students to follow along with at home. Modify if need be and enjoy!