It comes from the same hole as pee which is why people assume its pee or it smells like pee or has traces of pee.
The most effective way to get a woman to squirt is g-spot/clitoris stimulation.
Stick your finger in her vagina in a 'come here' motion and that little squishy mound at the top is the g-spot. Massage, lick, twaddle, (whatever, just do what she likes) and you should feel it swell up. That's building up juices and once she lets go and climaxes the juices will flow. It might shoot across the room like Jada Fire or it might just dribble out a little bit.
If you try it, report back your findings and let me know how it worked.
Also this works for women if you've never experienced an orgasm