Avril is wearing a wavy, long blonde hair style.  This is a very popular hair style these days.

And for those that don't have beautiful long hair like Avril's, you can go and get hair extensions and have a beautiful look in just a few hours.

To create this style, apply a curl-enhancing product all over the hair.  Blow dry using  your fingers and a diffuser.

If you don't have naturally curly hair (or have a perm), you can create curls and waves all over using a medium barrel curling iron or hot rollers.  For added dimension, use several different curling irons with different thicknesses and alternate them throughout the hair.

Let curls cool completely before touching them.

For extra help in keeping certain strands in place, apply hair spray where needed.