The right way to hold a mouse (in the sense of "most ergonomic") is the one that allows the hand to be an approximately straight extension of the forearm. In real life it is not uncommon to see the hand too far outwards or upwards, and fingers tend not to be allowed to curl up as much as would be desirable (which is why I don't like very high and curved mice much, or other shapes posing problems in that regard). In addition, common scroll wheel positions are utter fail, for they require a finger to be moved upwards.
For obvious reasons, the interaction of mouse position, mouse height, body dimensions and sitting height will influence hand - forearm angles significantly.
I've been using a Logitech G700 for a month and it feels like an extension of my forearm and hand. It's the most comfortable mouse I've ever used and the first one I've ever really used a palm grip on. I've been getting used to a palm/claw grip on the G700 for gaming.
For gaming on other mice, I use the fingertip grip. That's because I got into FPSs using the
Razer Boomslang. I also use the fingertip grip on my Logitech Anywhere Mouse MX.
For a long time I've used a 3M Precise Mousing surface with a gel wrist-rest (
link-also available in a larger version). With the G700, I can keep my wrist stationary on the rest
and use a palm grip. Side-to-side motion is accomplished by pivoting my wrist and I move up and down by retracting my fingers or moving my elbow slightly back. The side-to-side motion is basically linear because the arc would be wide. (At 2500 DPI, I traverse about one screen per inch, sometimes on three monitors. If the sensor were pivoted all the way around, the circle would be 8 inches in diameter, or just under 25 inches--62,500 pixels, in circumference. One inch of angular motion then translates to an arc of 14.4 degrees, for anyone keeping track.) There also seems to be some correction going on that keeps the cursor path "flat."
Sensor/mouse ball location becomes important when choosing a mouse based on grip style. Finer control is more natural when the sensor is closer to the fingertips. Razer mice have sensors in the center of the mouse, and the Boomslang has its mouse ball/sensor all the way at the back. The buttons are actuated toward the bottom, and the rest of the mouse basically acts as a stabilizer. With the DPI set low I also find it great for fine work in Photoshop.
NB: NEVER use a "memory-foam" wrist rest. Instead of supporting your wrist at the bone, memory foam gives into the bone and puts pressure on soft tissue. That soft tissue includes blood vessels, nerves and muscles..