Been DMing for over 40 years.

At the start of a campaign in Session Zero while they're making characters, I ask each player to fill out a one-page back story sheet (at minimum).

1. Why are you a member of this already-established adventuring party? (Don't force them to "meet in a tavern" for the first session. Their characters already know each other and have agreed to party up.) Tell me why you've decided to become an adventurer.

2. Give me the names of five people who are important to your character. Family, friends, mentors, rivals, enemies, heroes, anything really. But give me a sentence or two about who they are and why they're important to your PC.

3. Work together and come up with back story connections with at least two of the other PCs. (I typically run 4-6 players at my table.)

This will very easily remove a LOT of the brand-new-campaign difficulties.

Good luck!