So I am forever looking up this code.

Code

_required.scss

div.input{
    &.required label:after{
        content: "*";
    }
    &.error{
        padding: 10px;
        color: #B94A48;
        background-color: #F2DEDE;
        border: 1px solid #EED3D7;
        border-radius: 4px;
    }
}

This will add a star after any required fields, and also give a nice error style.