Part of being in love means being completely open to the other person. If you find yourself seeing a whole different side that the person doesn't show the public, then that may be love. For instance, if your partner is pretty serious or polite in public, but shows a more goofy and silly side when you're alone, then they are really opening up to you and loves you.  If the person shares their deepest emotions with you and is comfortable with it, then that could be love.  If the person is comfortable not looking perfect, tripping, or having food stuck in their teeth around you, that means they are okay if you see every side of them. This should be true even during a bad day. If your loved one has had a very bad day but lights up when they see you, then that's a sign of love. If they are in love with you, then the sight of you or the sound of your voice is guaranteed to make them feel better — if only a little bit. The next time they're grumpy or have a bad day, see how they react in your presence. Though this may be silly, check out your loved one's face the next time you see them. Do they look at you in a goofy, watery, silly and adorable way that can only be described as "googly-eyed"? You will know it when you see it. You won't get this look all the time — you can spot it in the morning, or randomly across the dinner table. You may also be able to catch the person staring at you with the same expression. Love makes people feel giddy, weightless, and like laughing for no reason at all. If you see the person acting this way in your presence, then this may be love. Does your loved one seem hyper, excited, and on the verge of laughing for almost no reason at all whenever they are around you? If so, then this may be love.  If you've said something barely funny and the person cracks up, then they may be lovesick. If the person shows nervous energy or fidgets around a lot around you, then they may just be excited by your presence. If you are suffering unbelievable emotional pain or are just bummed because you have the flu, then this should rub off on the person who loves you. If they truly love you, then they'll absorb some of your negative emotions and will be very upset because they'll want you to feel better as soon as you can. Though they don't have to be as upset as you are, the person should clearly be affected by your mood because all they want is for you to be happy.

Summary:
See if the person can act naturally around you. Gauge if the person is happy to be around you. Notice if the person gives you googly eyes. See if the person is giddy around you. Ask yourself if the person is upset when you are.