Gregster6: I always get it this way (you gotta actually catch fire each time) just takes lots of go's. 20 maybe?
15. You need to suffer incineration 15 times. The campfires are the easiest way to do it. Set yourself on fire, wait for the flames to die down, set yourself on fire, repeat.
15 times always works for me.
callofstalker: I think i found how to get one too, i've been smashing training dummies for a while and then i got the experienced ability. I don't know how many did i smash but i've been smashing them since the prologue and got the ability in late chapter 1(after meeting with letho in the elven baths) so it must be over 10 i guess since some(maybe all) of them respawn after a while and i smashed the respawned ones too.
B0stra: Tested it out. Seems you have to destroy 10 different training dummies. (5 in the "king summoned me" part of the prologue, 2 by the non human exit of flotsam, 2 by the market exit, and 2 inside loredo compound, or anywhere else you can find them)
Confirm 10 dummies. There are 2 more in the Flotsam garrison building, on the second floor. Do not advise you use your sword on them, though, because the guards in the building are not going to be happy to have you draw a weapon on their turf. What you can do is put your swords in you inventory, don't wear them on your back. Pressing 1 will then put Geralt in a fist fighting stance and you can punch the dummies. The guards won't bother you then. Be warned that Geralt does crap damage with his fists and sometimes he won't get out of his fist fighting stance until you're almost back out the door.