If a person likes you then most probably he will stand close to you without realizing. By invading your private space this person will think that he is getting closer to you. See Private space in body language.
According to body language a person's back becomes straight when he feels happy. If a person likes you then most probably his back will be straight around you. If the person's back changed from curved to straight when you arrived then it's a more powerful sign. see Body Language of the back.
If a person touched his brows after you said something then this means that the thing you said appealed to them. If a person touches his brows often in your presence then it could be a sign that this person likes you.
If a person is interested in someone he will Face them with his body while talking to them. If a person faces you in such a way that both your shoulders and his shoulders are parallel to each other then you can count it as a sign .
If a person likes you then this person will keep you in his line of sight as much as possible. Even if that person was standing far away he will still face you with his body to keep you in his line of sight .
If a person smiled to you then the muscles around his eyes should move. If a person smiled with his mouth only then the smile might not be that genuine. See The genuine smile Vs Non Genuine smile.
When a woman finds a person interesting she might toss her hair backwards revealing parts of her skin. If this gesture was done more than once in the presence of a man then this woman might be interested in that man.
If a person likes you then most probably that person will point towards you with one of his toes even if he was sitting far apart .
If a person likes you and you said something that made him smile then his smile will last for sometime. The more the person keeps smiling the more likely is it to be a sign of interest .
If a person likes you then he will keep gazing at you while talking more than the usual. A prolonged gaze is one of the universal signs of interest .
According to body langue a person's pupil dilates when he sees something that he likes. If a person's pupil dilates in your presence then this might be a strong sign of interest .
In early stages people feel anxious around the ones they like. If a person always felt anxious around you but was confident when dealing with others then there is a big chance that he likes you. see the body language of anxiety.
If a person likes you then his eyes might shine in your presence.
If a person likes you then he will look at back right after saying a joke to check whether you liked it or not See also what makes a joke funny.
A person who likes you will very likely become hyper active in your presence or right after you leave. This hyperactivity is usually caused by happiness.
When a person likes somebody then most probably he will mention him in his absence. In such a case that person will try to talk about his crush by saying anything related to him even if it wasn't a compliment.
If a person likes you then he might put himself with you in a group as he speaks. For example saying something like 'Me and Janna like swimming' or 'We both like Italian' are examples of grouping that could indicate the presence of interest.
If a person treated you nicely one day then negatively in another day in random manner then this could be a clear sign that he is changing his strategies to attract you.
A person who likes you will most probably spend much of his time getting your important goals done. If someone is sacrificing a lot of his time for you then it might be a sign of interest.
If a person likes you then he will hardly get bored in your presence. While there are many possible reasons for yawning some body language experts claim that it's a sign of boredom. If that theory is true then this person will hardly yawn in your presence. See why do people yawn
If a person is into you then he might complement you often. While the absence of this sign is not an indication of anything it's presence usually indicates interest .
According to NLP , neuro linguistic programming, a person will mimic the body language of another person unconsciously if he finds that person interesting. If a person mimics your gestures then he might be interested in you. See Why do people mirror others
If a person likes you then most probably he will change his schedule to bump into you more often .
If a person is interested in you then he will keep asking questions and as a result a conversation with that person might take longer than expected .
If a person likes you then he will use your name more often. People usually feel better when they call the ones they like by name .
If a person liked you then he might become more interested in your hobbies .
If a person liked you then he will try to find any other excuse to meet you again.
When a person likes another then he might try to find a nickname for that person. Usually people don't do that for the ones they aren't interested in .
If a person is into you then he will remember all of the small details you mentioned while talking to him .
If a person likes you then he might try to find any excuse to call you for even if it was something irrelevant or unimportant .
According to body language if a person saw someone who looked really good he might raise his eyebrows in surprise as soon as he sees him. (See the body language of surprise)
If a person likes you then he will smile for no reason in your presence. The more the person smiles the more likely it is a sign that he likes you.