I can't believe it took me 1000 hours of playing to learn this:
When your sim is talking to another, if you click on "more choices", you'll go back to the type of interaction circle, but if you then click on "romance" for example, and click on "more choices", you can keep clicking until you get the option you want (like propose or passionate kiss). It really helps if you're in something like the scientist career and have to "discuss work" or "gossip about co-workers." I was going crazy trying to get exactly those options to show up, until I found that I could make them show up.