I collect ideas from my reading, especially reading fanfiction. I find a character that really appeals to me and analyze why this is so. Fanfiction is great for this because you can look at lots of writers' subtly-different versions of the same character. I find relationship development patterns and think about which would be the most fun to write about. I have several notebook pages that are just a list of fun plot devices, like: truth serum, lost bet, taken prisoner, soulmate-identifying spell, heat cycle, gift of an origami flower, language barrier, mistaken identity, mind in wrong body, character initially perceived as animal/dangerous, etc.