Sienna Miller has worn her hair in many different ways.  She has been seen with a long hair style, very sophisticated updo hair style and now, a medium hair style.

To create the hair style shown below, you will need a medium length hair cut with very long layers all over and some side-swept bangs.

Apply a curl-enhancing gel throughout the hair and blow dry using a diffuser attachment.  If your hair is naturally wavy, you will probably not have to do much more than that to create the all over waves.  If your hair is not wavy, then you may have to use a curling iron to add the waves.