It's actually quite ingenious. Tell your significant other that you want to see if they have any idea what you are getting them for Valentine's Day, so why don't they take a few guesses? Let them know that your steely poker face is not because they are right or wrong, it's just that you don't want to spoil the surprise. They start guessing, you remember what they say, and you have a list of what they want.

This is an especially good trick for people who don't listen to much of what their SO says during the rest of the year. You're welcome.