Joint Placement: Clavicles

Most people's first instinct is to pivot the clavicles from the top of the sternum, which is only sensible as that's where the clavicles pivot from in real life.

And if you were rigging a really, honestly, realistically proportioned human character with corrective systems emulating the muscles and such, that would be right. But 9 times out of 10 that's not the case, even if you might think it's the case.
Look at this character. Looks pretty accurate to reality, no? A reality in which people have time to work out, but still.

Well this is what I mean by something feeling real rather than looking real. Because these shoulders? Real though they feel, they are not so.
Commonly the resting pose of a model (the pose in which we rig them) has a character with their shoulders pulled quite far back:

But this isn't where our shoulders really are when we're relaxed. For most of us they're quite far forward. None of us really walk around like this, do we?:

Maybe we should. It looks like good posture. But it's not something we're used to seeing in real life.

So what? So the model has an uptight idea of what 'relaxed' looks like, it's still anatomically accurate, isn't it?
Well when we pull our shoulder back that far, the silhouette of our shoulders narrows noticeably:

But character models' shoulders often don't do that. They have their shoulders pulled back yet from the front they have a silhouette that we only have when we relax and let our shoulders slump forward. Because that silhouette is attractive. But from the side, having the shoulder pulled back is attractive. So with any stylistic license, that's often one the first 'cheats' to happen to a character's anatomy.
As a result, if we really did let the model's clavicles pivot from the front of the chest like in reality, when the character did move their shoulders forward, they'd have some crazy wide shoulders:

So even if it looks like you're rigging a character with a "realistic" art style, ask yourself if it's really realistic or if it just feels realistic. Are this character's shoulders really where they should be given how pulled back they are?
If yes, well then - shit - place the clavicles at the top of the sternum. Have fun.
But in most cases, the way we accommodate these illusory, idealised shoulders is by placing the clavicles further inland, more in the centre of the chest, though still 'behind' where the clavicles would be normally:

Why don't we just do real clavicles? Because clavicles don't look like clavicles in the movies!

This is one of only several ways "realistic" looking characters are really only realistic within the visual standards of their own world. Most "realistic" looking characters in videogames, if you look more carefully, really have much longer legs than real humans, smaller heads, wider shoulders, thinner waists, etc.

So unless it's a project with attention towards technical anatomical realism, just assume to put the clavicle joints in deeper towards core of the upper chest: