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.

I got the strong stomach ability just from drinking the mongoose potion during the kayran quest

It turned out to be a useless ability as it doesn't give +%10 on quest experience and most of the monsters/humanoids you kill give less than 10 experience points. Might be a bug or it might just be the way it was supposed to be. Either way CDPR should look into that, enabling us to get more experience from the quests with this ability.

http://witcher.wikia.com/wiki/Character_attributes

Hope this helps a bit

Oh god the experienced ability sounds necessary.

Resistance to Magic: +20% Resistance to Magic

I think i got that after getting buff from places of power (those that give you protection, not sign power or regen)
Not sure if it was because I used them often or because I did use another one before the first went off... ah, it was in Flotsam woods

Hope it helps

Edit: bad tag closing -.-;

maybe it's given on Iorveth's path when fighting Dethmold with Saskia?

Should be granted after 15 times walking through a fire.

No it is not, i gained the ability in chapter 1.

I did it in the starting camp in the prologue. Just keep walking in the fire and take care that you don't die.

Nice! Would be cool to know if there is another way to get the Abilities that are on the other path of chapter 2.

It is a nice thing to have side based abilities but each side should have an ability, for example if you don't kill Aryan La Valette you get +50 load capacity but if you kill him you get nothing in return. I let Aryan live in my first playthroughs as i don't like taking lives much(but i'll gladly take the lives of the likes of idiotic bigot townfolk of flotsam who kill the nonhumans if you give Iorveth his sword in elven baths) but because i wondered what happens if i kill Aryan( and also want to see Mary Louisa La Valette's tits) so i killed Aryan(but not his men) but after finishing the prologue and playing a bit in chapter 1 i gave up as the game didn't give me any path specific abilities, not having the + 50 capacity is bad but still, i can do with that but not getting any abilities? I certainly cannot play like this.

In the wikia article it is stated that strong back can also be earned by losing a fist fight.

Hmm... If that is the case i should continue playing that save, thanks for enlightening me :)

Mmm... i don't get "Executioner" letting Roche kill Henselt...mmm...wtf?