So there's 3 marks in the game
: This leads to generally horny dialogue or a fruity ah scene. I mostly have it so that, if you want to avoid doing the horny options, then you can!
: Options with this on them give you a "Dad End" flag. Not every dad end is implemented at the moment, but there should be 3 of these choices per route.
(Currently, Dad Ends exist in Jehu and Paul's routes. Some routes actually reduce dad end points by being too friendly with or discouraging your date from being interested in Richard.)
: Options with the spinning gears are important. These options are very important for getting the true ending and will often steer the story in a different direction- sometimes largely, sometimes more subtly. Ordinarily I'd make the true endings not so obvious to get, but... you'll se!
In addition to these, many options do actually set flags of their own so they can be referenced later. Sometimes picking the "horny" options sets a flag for a later sexy scene. Sometimes determining your preference will lead to a more tailored encounter later. Sometimes you get alternate dialogue based on what you've said and done earlier in the story.
As an added note, options that are in RED are warnings- whatever follows when you click on it is not going to be pretty. Be careful!
(I think I'll add this to the main description of the game, too)