Best Starting Point?

My game I am DM'ing the party was all strangers that headed towards the town and ended up working together because the town was under attack. We are playing Hoard of the Dragon Queen. Since then a few have gotten close as friends, and some are kind of indifferent to the rest of the party, but working together still.

My most recent started with a dream sequence that ended up as we were stuck in prison and broke out together

I honestly say it depends when the setting happened could have a happens in a small village where everyone knows each other and gets a if two people may allow it then you may want to characters to know each other but you may have that one person in the group who's from another part of somewhere else or it may be on a ferry where nobody knows each other

I prefer to let the player characters backstories dictate how and if they know each other. If one is an infamous thief from a certain area, maybe others from that same area may have heard of them, or if they lived in the same city maybe crossed paths. Or if a few know each other from similar backgrounds in their backstory, the other may just haphazardly end up meeting them during the first session, or no one knows each other and a mission needs a team and the towns guard takes adventures to do it and they got lumped together. As a DM I take their backstories and WHY they are where they are and from there dictate if they know each other and or how they'll meet and become at least some semblance of a party.

Coming together by circumstance. I once had a dm that started off with a few of the players and gradually added to the story over the course of about 2 hours, and we all united over a common enemy. This allows newbies to see how things work before jumping in themselves, and having everyone just happen to be friends seems unlikely.