PART II: TECHNIQUES
Once you've nailed down a home base to hunt from, there's a variety of techniques at your disposal. One of the most classic, and for a reason, is the whistle.
Unless you're wearing April O'Neil's yellow jumpsuit or something similar, you're going to blend right in with the other trillion New Yorkers on the sidewalk. It makes sense to use another sense to get a cabbie's attention, and taste is definitely not your best bet. So you go with sound.
What kind of whistle works best? Remember, you're not just competing with the cacophony of a densely populated metroplex. The driver is also shielded by his vehicle. More than likely, his windows are shut tight, to keep the stink in. (Or, theoretically, out.) Also, he's either got his radio blaring (either Hot 97 or conservative talk radio, usually, for some reason) or more likely, is arguing with and threatening someone via bluetooth.
This makes your best bet the Fingered Whistle, with at least two digits in your mouth to achieve maximum high-pitched annoyance. Drivers will pull over just to make you stop, or to see what kind of person actually hails cabs like that. But it gets the job done. Some believe the more fingers you jam in your mouth, the better. Some will even double-fist it. Find the ridiculous gesture that best suits your needs.
But don't use your rape whistle. That's just going to end badly for everyone involved.