1)Arch your back like a cat.1 trick can be to tilt your neck back.
2)Relax knees and do NOT lock them.
3)Bent over 45 degrees(There are many differeniating views on the angle but you should be back to feel the muscles worked at that angle.If not you can bend over somemore)
4)Pull to your naval.
5)Use a mirror to guide your form.(Side view)
6)Practise form with light barbell(discretion)first.
7)There are two grips.One is pronanted(Standard double overhand), another is supinated(curl grip).The latter is called a Yates row if i am not mistaken.
Click on 2nd mouse button on the image and press "Open"