Ever been in that situation where you thought someone liked you and it turned out they didn't? Or that you were absolutely sure you were just friends, and they turned out to have feelings for you? Guess what? It happens all the time, and yes, it happens to almost everyone. There are overt signs, and then there are the clues that you'd have to just know to be able to tell that they're interested in that way.
You know about all of their dates, you know about what they did, where they went, their first kiss, the whole spectrum of their experiences. If they ask you often about your own love life, this is also a sign that they're waiting for you to open up to them as well. This may seem counter-intuitive, but you'd be surprised how many people want the object of their affections to be jealous of their perceived "fantastic" love life. It's almost as if they want to show you what you're missing out on, and how much other people find them attractive. Another big sign: They don't settle down with anyone—if they talk about this great love life but never seem to find "the one," maybe its you they are really waiting for.
You always show up to the same get-togethers, make sure they are at the same events as you, and you wonder how they always know where you are. It's not done in a creepy way, but they hope to be around you as much as possible and ingrain themselves in your life in a way that you become dependent on them.
Where did all these serious topics come from? Weren't you just talking about your favorite TV show? If your conversations veer towards the self-important and very serious, then know that they feel comfortable enough with you share their deepest thoughts.
The eyes are the window into the soul. A cliché, but so true. If you find yourself being stared at or having that person keep giving you quick glances every so often, it's likely that you're the only person in the room they have eyes for. These lingering glances reveal a lot about longing and a person's feelings.
An extra long hug, a lingering handshake, anything that lets them touch you a little bit longer is a good indicator that they like you more than friends. If they get the chance to sit next to you, or at the same table, they will. If there are groups, they always end up in yours somehow. It seems that they always end up touching you in some way, either by a friendly hand on the back, or a high-five, just about anything to get them near you.