The are a several circumstances when you mark XP in Dungeon World. Other than rolling a 6-, you mark XP when you resolve a bond, play your alignment, or answer one of the three end of sessions affirmitively. I’m a fan of the latter (end of session questions). I’ve used it in other systems, and I plan on adapting it for Open Legend. Since answering three questions at the end of the session would level PCs very quickly in Open Legend, I’m going to break each XP into another currency that you use to buy XP (and idea that comes from Mage: The Awakening 2e and probably other Chronicles of Darkness games, which calls it beats). You can control how fast people gain XP by tweaking the cost. I posted some obsolete musings about it in another thread. The big difference is I decided to keep the legend point economy as-is. I want my players creating interesting situations by invoking their flaws. 
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