If you just finished the game, I'm sure ur thinking: "What now?" well theres plenty to do. Like, there are a bunch of super awesome secrets u can unlock by collecting the precursor stones. THe secrets include:
1.Infinite Dark Eco
2.Infinite Light Eco
3.Shadow Invisibility during Dark Jak 3
4.Infinite Ammunition
5.Invulnerability
6.Hero Mode
Those are super cool and useful! And if you cant find enough precursor stones, you can start the game over in Hero Mode with all of your weapons and abilities (except Dark Strike and Light Flight) and get the stones again.

The bad part of beating the game: There's nothing left to do besides start over again. It's depressing and lonely. Like, all of the main characters you can usually talk to have disappeared, so your only companion is Daxter, and he stops talking after you beat the final boss.

They're called Precursor Orbs, not Precursor Stones. And you can collect them by doing the side missions by going to the totems and kiosks across the two main cities and the wasteland. You'll also find orbs lying around the two main cities waiting to be collected (but not in the wasteland, only the orb challenges are there).

What i do is with unlimited fly jak i do the glitch ( press x and o repeatadly real fast and you can fly super high and stuff)(its most fun in the wasteland) and sometimes pretend some of the houses are handy manny's house ( most fun in the wasteland)or pretend the people in the wasteland are handy manny. pretend its like halo where you kill the guards or metalheads