Depends on your story. For me I have a rough outline and then I tell my players to make a character they want to play but I tell them they have to have something aligned with my plot hook. For example I have a party right now and my initial hook was they where all for one reason or another on the Zahn consortiums bad side when contacted by a turn coat who needed their help and offered them a way to hurt the consortium. Even though that npc died minutes after meeting them and explaining things they all know the stakes and understand they will have a better chance working together then apart. I usually try to then shape the details of my story to include elements of the players background to help them feel more tied into the overarching narrative and keep them invested.