Listen to office gossip. Word often travels fast if an employee has a crush on a colleague, and in some instances, you may be the target of someone’s fancy. This will allow you time to prepare in case the situation escalates beyond your comfort.
Make note of colleagues whom you catch looking at you when they think you cannot see them, or who catch your eye and display flirtatious behavior.
Check your emails. A colleague will often send you a high number of emails simply to prompt a response, or get your attention. If your inbox is dominated by messages from one person, this may be an indication of their affection for you.
Watch out for notes. A co-worker who has a crush on you may leave notes on your desk, sometimes disguised as business requests.
Similarly, a co-worker who is affectionate towards you may ring you to ask for advice or help that is unrelated to your job role. It’s a thinly-veiled attempt to talk to you.
A colleague who has a crush on you will often endeavor to ‘accidentally’ bump into you, or be in your physical presence. An example of this is heading to the kitchen at the same time as you, in order to be with you and prompt a conversation.
Speak to the person in question. While often they will be too shy to admit an affection, you may find that they freely speak of their crush on you. You can then deal with this information as you see fit, keeping in mind the well-being of both you and the other party.