How many sprays do you use?

I never seem to know how much is enough, though I have only gotten complaints when I wore a single dab of "LouLou" in a car. I go by five sprays, usually: two somewhere in the general direction of my hair, one in the neck, and small ones on both my arms. I wouldn't dare with "Fracas" though

Good question. It really depends on the fragrance for me. I think my sense of smell is not as sensitive as others or maybe my tolerance is greater.
I probably err on the side of more rather than less. I have a few fragrances where two sprays is more than enough (the Tauer's and maybe "First" and "5th Avenue") but generally I'll do two on each forearm, one at the top of my inner arms (in summer, as this area seems to hold fragrance better) and a couple around the neck area. I'm more generous with citrus/green perfumes than with the heavier florals/ouds, which can be claustrophobic and overbearing with over-spritzing.
I have a couple of weak fragrances where I never seem to reach the depth of scent that I'd like (reformulated Givenchy III and reformulated Fidji) but I think this is the fault of the reformulation where the fragrance is now thinner and with less body.
It doesn't seem to matter so much whether it's an EDT or EDP. I have a lot of EDTs that seem more potent than the EDP version of other fragrances. As this is a nominal classification of strength with variable parameters, I guess you can never really know which end of the EDT/EDP scale the fragrance is at.

I spray on the inside and outside of my wrists once for each because it seems to be the only place where I can smell it, and keep whiffing that area throughout the day. It puts me in a better mood.

I find that spraying my stomach and letting it dry before I get dressed gives me the most bang for my buck, as it wafts up at me all day. Depending on the fragrance, I need only one or two sprays there. With less potent ones I spray once on my forearms too.

I agree that finding the best number of sprays for each fragrance is crucial, because for some beautiful ones, less is more, and over-spraying can be very counter productive. And concentration is often meaningless. Coromandel is supposedly an EDT but is more potent than most of my EDP's. One spray to the tummy and I'm good to go.

Amount of sprays depends on the perfume. I can happily douse myself in 24 Gold all day and not feel overwhelmed or overwhelming to others, whereas Habanita I need to apply with a q-tip lest it become noxious.
As for location, with the average perfume I'll spray wrist, cubital fossa, jugular, all symmetry... 6 sprays total. This is a huge increase from when I started out.

For me, it depends on each perfume, the concentration, the temperature outside...these are all factors that are variables for the amounts of sprays or dabs.
If I were to use my Shalimar, a dab behind my ears and one on the back of my neck is sufficient. It is so very strong.
With some of today's current formulations, it seems I have to spray my inner wrist, my inner elbow, and spritz my hair to get any type of effect. That could be with any brand of today's fumes, regardless of the maker. There are always exceptions, specifically like Habinita or Dior Addict, where a little goes a long way.
And more often than not, with vintages, especially the heavier orientals, they are stronger and do not need much. They seem to grow deeper and develop a more intense aroma, which I like. Anne Klein II would be an example of that.