It's about giving the boy or girl a few moments to quietly and one-sidedly observe you. When someone pops up in your life out of context (ie. a coworker whom you've never seen out of the office is suddenly walking underneath your apartment window in a pair of cutoff shorts with a potted plant in his or her hands) you experience a second of disbelief and you want nothing more than to watch the person until he or she continues out of sight. No amount of witty conversation or alcohol can make a boy or girl take an interest in you like showing up where you shouldn't be and continuing about your life unaware that the boy or girl in question just saw you. You become the main character in a plot he or she must watch unfold.
So find out where the boy or girl on whom you have a crush lives or works and just walk around that area for like 7 to 9 hours. Buy something and carry it around so it looks like you're there for a reason. Don't spend too much time right in front of his or her office or apartment building or he or she might get freaked out.
The hard part is making the boy or girl you have a crush on want to touch you. It's tricky, because you can't know when you've been spotted because whenever you know he or she is around you start acting like you're fucking high. Just try to never stop being attractive. We're not saying put on a pretty dress or a slimming pair of shoes. This is about affecting a manner. Just think on a fond memory that puts a half-smile on your face that says there is something intriguing going in your head and it belongs to nobody but you. Or if you're waiting for the light to change, lean against the lamp post with a posture that says, "Man, have I been to a lot of funerals!" You need to just walk with such a pace so that when the boy or girl you have a crush on sees you pass by the coffee shop storefront window, he or she will be enthralled by your presence and will wonder what's going to happen when you turn the corner.