Dean- you and Dean met when he had to "save" you on a hunt

Sam- you and Sam met when you were in the library and picked up the same book

Castiel- you were on a hunt with the Winchesters

Lucifer- crowley turned you into a demon so you could let Lucifer out of the cage

Jack- you met when Sam and Dean brought him back to the bunker

Gabriel- he put you in the alternate universe with Sam when Dean died multiple times

Charlie- you bumped into her on the street after running away from an abusive home

Jo- she met you when she met Bobby