I think it helps to be young. Young with a degree of studied or educated carelessness. I won't use the word "sprezz" here or any of that nonsense, but I do think the guys that pull it off well are a little rough around the edges and have a degree of eccentricity to them. Almost as if jeans are the only thing they could wear with the look. I think Sid's employees do it well: The unstructured SC (which is a 3-roll-2 peak lapel, so let that simmer on its own for a minute), knit tie, floppy collar, hoof-pick belt and playful slippers all seem to echo a laid back aesthetic. Also, everything here has a more crunchy/unfinished texture. No shiny silks, no crisp edges, no mirror-shine polishes. I fear here (an other places) people try and pair a more structured, conservative SC or orphan that is made to be worn with formal slacks or as part of a suit with their jeans. The point to jeans is that they should be paired with equally casual accompaniments. It isn't the same relationship shared by odd trousers and jackets that can easily be mixed and matched.