Hey everyone. I'm new here and have been lurking for some time now. Just wanted to reply on my favorite topic. =)
I've squirted from both clitoral and g-spot stimulation, and I had to learn how to do it on my own. For me, it's a combination of the need-to-pee sensation, along with intense tingling around my g-spot. And I definitely can't have a toy inside of me when it happens. But my gf's fingers don't need to be out of me for it to happen.
In my experience, it was easier to learn how to squirt during clitoral stimulation. I paid attention to how my g-spot felt as I used a vibrator on my clit, and once I got to the point of no return before a clitoral orgasm, I pushed out. This allowed me to have multiple orgasms from my clit in between quirting, back to back, without losing any 'momentum'. The orgasm/squirting intervals lasted over a minute, and I never touched my g-spot. After that, I was hooked. But it took awhile to learn how to let go and have them with a partner.