The good ol’ fashioned “You all meet in a tavern, answering a poster offering gold for help…”? The action-scene, “You’re all engaged in mutual mundane task, when suddenly a band of thugs/goblins/whatever bust in looking for the plot coupon and chaos breaks out”? The “Elder Scrolls classic” - all being prisoners thrown in together? Tie it in to a character’s backstory and let them lead the other party members in?
What have you found interesting or successful, and why?
Depends on the characters, but my favorite was a prison break. Some party members were visitors, others were hired as support guards due to a dangerous inmate being transferred (BBEG) and one was a prisoner. Large boom and suddenly the prisoners are escaping and as the characters are all fighting to get out they get funneled together.