Among the "you'll know without having to ask" tips is No. 14:
They’re there for you when you’re sick. Not every day is filled with hearts, bells, and whistles. If you’re under the weather and this person at your side with chicken soup, flowers, and would rather nurse you back to health than hang out with their friends, it’s their way of saying that you’re a keeper.
And No. 17, among others, is also telling:
He gives you a key to his home. When you exchange keys with enthusiasm he’s letting you know that you now have the key to his heart.