Mouse speed too fast

1. Open a terminal
2. Run the command: xinput --list --short

Logitech USB Optical Mouse id=10 [slave pointer (2)]

(this is a part of output you will see, I found the name of my mouse Logitech USB Optical Mouse)

3. Note the name of your device.
4. Set the constant deceleration for the device:

xinput --set-prop "Logitech USB Optical Mouse" "Device Accel Constant Deceleration" 5

You need to play with with number, here 5. Don't loose focus of your terminal because mouse speed may become either too fast or too slow. lower the number the faster it will be, similarly, higher the number slower it will be. For me 1 is too fast, and 100 is too slow.

5. To see the current settings for the device:

xinput --list-props "Logitech USB Optical Mouse"

If this didn't work for you, you can always revert it back like this:

xinput --set-prop "Logitech USB Optical Mouse" "Device Accel Velocity Scaling" 1
xinput --set-prop "Logitech USB Optical Mouse" "Device Accel Profile" -1

reference

I ended up having to do

xinput --list --short

as said by original answerer, but had to do

xinput set-prop 17(my device id) "Device Accel Constant Deceleration" 2

to make it work on my Xubuntu 16.04 setup, because i have multiple devices matching 'Microsoft Microsoft Nano Transceiver 1.1' ..

If ConstantDeceleration is not available, you can use negative accelerations.

In Debian XFCE I used:

xinput set-prop 8 "libinput Accel Speed" -0.9