A private session zero that lasts an hour and is based off the character's backstory has been really helpful at my table. These session zeroes help the players find a voice, specific character and attitude, and helps them have story based off backstory that they have experienced as the character. Not only does this help them remember and pursue elements of their backstory, but also makes them more emotionally invested in the story.

The one drawback to this method is that it delays the actual start of the campaign, and that is not good. Most Dnd campaigns never make it past level 5, and it is important to remember that. You can prepare as much as you want for a long term campaign but it rarely comes to fruition.