The answer from Umar Soleh is excellent. This answer is just to point out an alternative which is a bit more complex, but more comprehensive because you have access to additional settings that
Tweaks does not expose.
1) Install Dconf-Editor. From the Terminal:
apt-get install dconf-editor -y
2) Open Dconf Editor and accept the warning to be careful!
3) Find touchpad settings at
click-method; turn off
Use default value; set
Custom value to
fingers [Umar suggested
fingers which for me feels the most natural]
You may be interested in other settings in this section (along with my personal recommendations):
* send-events: Set to `disabled-on-external-mouse`
* tap-and-drag: Disable (an annoying feature!)
* two-finger-scrolling-enabled: Enable (the default)