@Carl:
I use Window's search for the tuning files too; it works reasonably well for XML files. For the tuning descriptions and the script files, on the other hand, I use the multi-file search of Notepad++, since the Windows search doesn't seem to find things inside those files.
(BTW, I make sure the file name of the extracted tunings include the name, the hex ID, and the decimal ID. Then I can do a far quicker search for the file that defines something by searching for "file:*<name or ID of what I'm searching for>".)
I'm trying to find what makes Woohoo available. From what I'm seeing it's basically having a romantic relationship at 30 or more, having already had the first kiss, the two sims not being linked by blood, and a few other more or less default tests (target sim not being the grim reaper, not being pregnant and in labor, things like that). Simpler than I expected.
For kisses (and other romantic interactions) it's more complicated, and you need to look at each specific interaction file (and tests linked from that file) to get a good idea.
The short version is that it depends on mood (no kissing while angry or sad, for example), relationship (married, engaged, girl/boyfriend, etc), and the score obtained in the file scores_socialoutcomes_romance_availability (similar to the one for the results of romance, which I posted previously in a far more readable format, but with far less things influencing the result). Those scores are such that the test is almost guaranteed to pass if the sims are in a stable relationship (significant other, engaged, or married) or have the romance bar above half, BTW, otherwise you want a romantic conversation (preferably Steamy); all other scores (including for the Flirty emotion) pale in comparison, and you need to pile up a bunch of them for them to have any effect.
The long version is that you need to look for the tag "test_globals" inside each interaction file, there you will see references for many kinds of test, including for a score (test_based_score_threshold tag), relationship tests (i.e., if they have met, are engaged, married, etc), mood (many romantic interactions seem disabled if the sim is angry or sad, for example), buffs, and even whole lists of tests from another files (the tag test_set_reference). Do remember that one or more of those tests can be inside a referenced file; usually the score and relationship tests are grouped like that.
@arcadiana:
Sorry, I don't know. But AFAIK the gender preference is flexible, it will change if the sim keeps having romantic interactions with the not preferred gender (and the sim might even end loving both equally). I would go for romantic interactions that don't get rebuffed for a while, until each sim starts accepting the other's interactions.
Of course, if the two sims are related by blood, you are fighting against the incest block. AFAIK the only way to get two such sims to engage romantically is with mods.
