Hi All... when should i start my baby on solid...

Hi All... when should i start my baby on solids. My son is 10 weeks old - and hungry. He has 5-6 200mls of formula daily, and wonder if i should start him on a spoonful of farex (or something similar) now, or is it too early? One of my girlfriends started her son on solids at 12 weeks, but i'm not too sure.... Any advice would be welcome. ta