Just a few more things that possibly could work, dance machine trait might make them show up at dance clubs. Put them in the same gtw style career. Hire one at a restaurant or retail store and go there with the other.
And maybe pay attention to their traits and go to locations that would attract that trait, for example, romantic sims at the romance festival, geeks at geek con, art lovers at a museum....
But one sure fire way is to put the sim in a club and select a specific venue as the club hangout. That club will show up at that venue from time to time while playing your other sims.
