Exactly!
With scroll button:
Index left.
Scroll middle.
Right ring.
Thumb and pinky fall over the sides of the mouse so that I can pick the thing up easily.
Without:
Same as above except the second finger rests on the left button.
The mouse I’m using right now must be pretty small. My last finger joints are resting on the very edge of the buttons and the bottom of it is tucked into the mound of my thumb.
Hold mouse firmly in right hand, move pointer by waving mouse in air with my index finger on the trigger, all clicking and scrolling done with my thumb.
Yup, it’s one of these babies.
Same here.
And yes, I hate sitting down at a computer with a scroll wheel-less mouse.
I grasp it like you would a phone and left click with my thumb. Thumb also scrolls, and my index finger does the much despised right click. To move the cursor up, my hand moves to the left. My arm doesn’t get tired as fast this way. btw, I wish I had one of the mouses htns has…mine has a ball…
I use my index both to scroll and to click the buttons.
Index finger on left button and scroll wheel, middle finger on right button.
I use a pen and pad - Wacom Graphire. Mice ought to be banned.
Scrolling and left-clicking with index finger and right-clicking with middle finger.
Left Click: Index finger
Wheel: Middle finger
Right Click: Ring finger
What the hell is wrong with the rest of you? 
I myself like the ms trackball (the cheap one with the thumb ball). Thumb goes on the trackball, index goes on the left button (and the ‘back’ button), middle finger goes on the scroller/middle button, and ring goes on the right button (and ‘forward’ button).
When playing Unreal or Quake or somesuch, I use the Explorer, with fingers arranged the same way.
I’m thinking I’ll have to try the pen and pad some day, that sounds especially groovy.
My computer doesn’t have any index fingers. Am I missing out on something?
Left button and scroll: Index finger
Right click middle finger
Using one of those “handed” microsoft mice which is quite assymetric I don’t see how a non-mutant could use a three finger technique on that. My fingering is affected by a busted knuckle so my fingers don’t spread out evenly. This also means I can’t do the live long and prosper salute with my right hand 
.
Thumb. I have a Microsoft Trackball Explorer thingie…
lower left button - left click
scroll wheel - scroll
scroll wheel as a button - copy
upper left button - enter
upper right button - paste
lower right button - right click
I love my trackball…
As do I
tanookie … you are unique but not totally alone … i have adopted the following method for the past 15-20 years (10 hours+ daily) … this posture serves me well.
basic microsoft* device (right-hand, two-button, scroll-wheel) …
thumb cradles 'n controls left-rear of mouse-body …
index-finger is vestigial and relaxes against left-front of mouse-body …
middle-finger rests on left-button …
ring-finger rests on right-button …
pinky cradles 'n controls right-rear of mouse-body.
scrolling? simply use the pointer on which ever window is in focus.
why? matter of environment 'n ergonomics … as well as habit.
regarding omission of scroll … my work-place had old mouse … scroll-wheel failed to make good contact … so i did without.
regarding middle-finger on left-button … had case of tendonitis occurring in my right-hand (index-finger would seize) … started using middle-finger.
additionally, with respect toward ergonomics … i also utilize wrist-pad to elevate my wrist … nearly level on same plane as my fingers.
*Microsoft-Wireless-Mouse-900
You know Tanookie posted that nearly 13 years ago and hasn’t been active since 2005.
Using the ring finger seems very strange to me, but I wonder if this breaks down to when people first started using mice.
My theory:
When I frequently started using mice (early nineties), there were two buttons and no scroll wheel. Pretty much everyone used their index finger and middle finger. Once those fingers got used to their positioning and job, adding a scroll wheel was unlikely to change it.
If you started to heavily use mice after the introduction of the scroll wheel, having three fingers on it would seem to make sense.
I use either, depending on context. My normal mouse grip is index finger = left button, middle finger = right button. If I’m going to scroll a lot, I switch my index finger to the wheel. If I’m going to be scrolling a bit and clicking along the way, I switch the middle finger to the wheel.
I don’t think about this at all, and only know it now because this topic came along and made me actually pay attention.
It’s rare that I need all three inputs at once, and three fingers on the mouse at once is pretty crowded, and when a program tries to make me do that, I generally remap one of the functions involved to a key or something.
Right handed, however…
I use the mouse left handed, index finger on the scroll wheel and middle finger on the left click button. Makes it easier to type right handed and use the mouse at the same time.