They make fleeting eye contact
They obviously see something they like but are hesitant to approach you--let them know you're interested by staring at your iPhone and refreshing your e-mail inbox seventy-two times.
They make eye contact for more than five seconds
Whoa, this is getting serious--seriously HOT! Maintaining eye contact is the largest indicator that someone is romantically interested in you - or you're engaged in a really intense staring contest - or they are a deer.
They ask you where you are from
They obviously want to know all about you. Start by telling them EVERYTHING: where you grew up, what your favorite subject in school was, who your favorite Spice Girl was, how you rank the flavors of Starburst, what 9/11 conspiracy theory you believe, if you have a general disregard for the Oxford comma or believe it to be a fundamental building block in sentence structure, if you prefer McDonald's or Burger King French fries, etc. Of course, in between each fact about yourself you should be shouting, "I'M A [your astrological sign here]!" at the top of your lungs.
They ask you what you do
They are interested in your career endeavors and the general trajectory of your professional life. Start by saying you do a lot of things--then start plucking a sitar and explaining string theory in detail or showcasing whatever skills you have that can best be described as "eccentric." Impress them!
They offer to buy you a drink
Even the socially inept knows what that means (FREE BOOZE).
They ask you why you keep telling them they have gorgeous hands and could be a hand model
WAY better than boring ol' "you have nice eyes" and way more memorable! Keep giving them unique compliments (example: Your hair is shinier than a freshly installed solar panel!) and they'll never forget you!
They tell you to stop texting them
That just means they want you MORE.
They say they want to "just be friends."
The subtext of "just friends" is "try harder!" Don't be scared of a challenge!
They file a restraining order
They're playing hard to get--cute!
They call you "buddy"
Everyone knows the universal protocol for when a prospective romantic interest addresses you as this: call the police.