There are many tell signs that you can look for out. Here are the most common and obvious ones.
Frequency of running into each other - You would meet him more often around common areas of the office like the cafeteria.
He hopes everything else when you walk to him - He stops working on everything and starting talking to you when you walk to his desk and never is busy for you.
He talks good about you - When he speaks to his friends in office, he also has a lot of praise for you.
He wants you to have a good impression about him - Tries his best to leave a good impression by telling his professional achievements, interests and lifestyle.
His friends and you - His friends behaving differently when you are around.
His smile - He smiles at you in a very friendly way every time you bump into each other.
How he gets introduced to you - He would generally get close to one of your close collections and later get introduced to you through them.
Jealousy - He gets a little uncomfortable when you interact with other co-workers in a friendly manner.
Keeping in touch - It would keep in touch with you on a daily basis.
Office Parties and normal weekdays - He generously offers to pick you up from your home when going out for office parties or requests if you need a drop home.
His parking habits - He parks your cars right next to yours on most days so that he has a chance to talk to you.
Relationship Status - He makes you understand that he is single and looking.
Someone outside your team - He may be in another another in that team probably would never work with yet find a things way to meet you can talk to you during break time for coffee or lunch.
Wants to know more about you - He makes an attempt to understand you better more from your likes, dislikes, what you like doing, favorite food, etc.
Your safety - He calls you or texts you to check if you are home safely.
