How do your sims find someone that they really have a good romantic chemistry with?

I'm in the same club as @So_money and @Netzpannung, I generally make the decision based on how the sims interact on their own. Where I get in trouble is when I overthink it myself...as evidence by a recent thread where I asked for help from the forums. If I just let my sims decide and then run with it, they do a decent job.