Fria Ligans forum

If they are aslene or alderlander or.. etc
How much should they know about the history of their people??

Besides whats in the Player's Handbook, I let them know the basics of their kin, or just their group/clan when there are more than one. For example, one of my players played an elf once, he became an elven warrior so I let him know his background (as a Redrunner) and also about the ruby. I told him some vague information about the other elven groups, but not much.

Thanks. Yes that’s what I thought. Give them a bit of background of their people. But it’s hard to know where to stop...

I let them know the specifics of their kin (so they can roleplay well) and some history from the perspective of their race, handpicked by me depending on the story I want to tell.

I made a religion hand out for my group so they had a hot clue... I figured they would at least know that.
Working on a Kin handout to give them the basics... everything else they'll find out in game as I had them get exiled over the Iron Lock in their first session.

Recruit em into a cult and fill their head with rumors

I give them almost zero exposition, instead I say that any questions about the setting can be answered by succesful Lore checks. Holes in their knowledge are explained through background, eg if they are playing a dwarf and fails to learn what god dwarfs believe in, then maybe they are playing a dwarf atheist, or a renegade or an exile or whatever. By using lore as brain google they will have to actively ask for setting information, and are hopefully gets more vested in it. 

I don’t plan on giving much beyond the bloodmist to anyone except perhaps an Elf or Dwarf. And even then keep it pretty vague. I’d explain kin rivalries in only the vaguest possible way.