Wow, I didn't know anyone debated that girls have G-spots. We definitely do! It's not something to "believe" in. Feel around on the inner wall of your vagina, about 1-3 inches in. It is on the vaginal wall closest to your front, so you'll have to curl your fingers in a "come hither" gesture to feel it. Try getting a dildo or vibrator if this is uncomfortable for your fingers. You can also get a partner to help you out. I find that doggy style is the best position for hitting the G-spot. It feels fantastic! When you stimulate the G-spot, you may feel like you're going to pee, but keep going. You won't pee, but you might experience female ejaculation. I've never ejaculated myself, but those who have tell me its great... I'm working up to it...
