Looking at the palm side of my hand, the first knuckle-crease on my middle finger is barely visible as I can feel the lower edge of my wife's g-spot. The second knuckle-crease is barely still visible as I reach the top of her G-spot. Any farther in and I begin to round the top of the pubic bone, just above which is a spot that feels similar to the G-spot, but is smaller and less grainy(?) that I believe to be her A-spot.
Unfortunately, her birth control and some other medications have rendered her A-spot out of order, and her G-spot has never been able to get the job done even though she can occasionally squirt (just not as part of an orgasm), but it still adds a lot to a clitoral orgasm.
To those of you still trying to figure things out, don't give up. My wife initially took 45 minutes to climax through direct clitoral stimulation, but now averages maybe 5 minutes, with a best time of a minute-ten. She learned to have A-spot orgasms after that and could climax in just a few minutes that way, also.
Breathing techniques, kegel-flexing, position....all these things will have to be figured out for you to find what works for you, just keep at it. Once you get it, it will most likely continue to get easier for you to do it in the future.