
Even small pre-established contexts can help push characters to interact - it doesn't always have to be "our characters were childhood friends all along". It can be as simple as "my character saw yours at [place] last week", because then that means my character knows yours is a [profession related to place], and can strike up a conversation about being/needing/etc a [profession]. It's nice to mix and match "missed connections" introductions like that with the more typical "cold call" introductions.