Marc Mendicino - Style Director, Australian Hair Expo Men's Hairdresser 2009 and in Salon Educator at é SALON has some great tips to help no matter if you are using a GHD, VS Sasooon or other straightening irons at home:

General tips:

Always ensure your hair is completely dry before using the irons, never use heated staightening tools on wet hair unless manifactures instructions say you can. A heat protective spray or styling product like Kerastase Voile Protecteur applied to each section just before straightening will protect yoru hair from damage. 

Use section clips to divide your hair into 4 sections (2 back and 2 at the front). Work through each main section in approximately one inch thick sub-sections from bottom to top, this will ensure you do not miss any hair or get lost whilst your working through.

How to straighten:

When curling with the irons still work horizontally to the head as you would with straightening, but over direct the hair up and away from the head for lift and volume at the roots. Draw the iron a short distance along the section and then with a flick of your wrist twist the hair in the iron back on itself 180 degrees. In one smooth, slow action now draw the iron whilst twisted in this way along the hair to the ends. Once through the entire length of hair, twirl the section around your fingers and leave to cool in the ringlet shape you have formed. The slower you draw the iron through the hair the tighter the final curl result will be.

How to curl with a straightening iron:

Always work the iron horizontally outwards away from the head. Section the hair up into manageable sections no wider than the plates of your iron. It is best to do this by dividing the back into 2 sections and front into 2 sections above the ears. Start in the nape of the neck at the back and above the ears at the front and work up. Slide the iron slowly and evenly along each section as you work keeping the iron flat. Slightly round the iron off through the ends for a more polished finish.

- Don't try to curl a section bigger than one inch squared.