Drinking naturally opens you up to 1-night stands. Much of the H-content is found in the various Jobs, clubs, and relationships you can find around the castle. Anya has several that you see from spending time with her, Andrew and Eillana are the same with that.
Attending any job or club gets you stats in addition to attending classes. In particular church work gets you will (eventually). You can also repeat classes to continue getting stats from them (and the wiki, I think, has stats listed for much of them.)
Mana manipulation 1 (one of the first classes) gets you +1 will
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Much of the game's H-events are listed here
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Though it is a bit out of date (you can check the game's changelogs on the first page to see some of what was added more recently)