I have done long long mermaid hair, shorter, chin length hair and pretty much everything in between. I always LOVE LOVE LOVE my shorter hair, but about 3 or 4 weeks in I start to miss the versatility and ease of just being able to throw my hair up in a pony tail or messy bun and begin the long process of again growing it out. About 2 years ago I discovered the awesomeness of pinning my longer hair into a messy bob for the day. No more craving shorter hair since I can play with it for a few days then go back to long, easy hair.
The secret is having layers that are the length of the bob you want. Specially in the front. Mine are between shoulder and chin length.
Some gentle teasing around the hairs on my neckline and some pins are all I use. Just pulling three or four sections up in total. I simply tuck the hair under then secure with two pins criss crossed over each other and it seems to hold all day!
A little messy length in front keeps it fun and easy to pull behind my ears.
You can adjust and play with it until it feels about right, there's no wrong way to do it
And now I am patiently going to wait a few more washes for my hair to tone down to the perfect pastel (oops! got a little carried away with the last colour touch up LOL).