today's general rule is this:
If he commits an unexpected and thoughtful act of kindness for you, that means he likes you.
because men don't do such things regularly, the way a woman might. women are prone to think about you and pick up a card, a small gift, or your favorite [insert noun]. women are caretakers like this, and their thoughtfulness comes so naturally to them.
not to men. men don't usually just think of you while they walk around the grocery store. men usually don't happen to be at Hallmark and see a card that seemed absolutely perfect for you. if he's thinking about you at a time when he's able to pick up or buy something for you, that means that he's thinking of you constantly. the random act of thoughtfulness from him means that he can't get his mind off of you.
having shared with you that general rule, let me share with you the specific one that inspired me today:
If you text him to complain that Target is completely sold out of Bridesmaids on DVD, and his response only 4 minutes later is, "I just bought it for you on Amazon. It'll be here in 2 days. Come and get it." that means he likes you.