At this time, 2018-11-24, Buster is Testing.
This can change in the two months before it becomes Stable.
I had written this article on how to get tap to click on Debian 9 about the same time frame, and it worked then.
This does not work on Buster. When I tried it this morning, rebooted, and was presented with terminal only and a login screen. Removing the files that I created got me back to where I was.
I am doing this on a Lenovo Thinkpad X1 Carbon Version 2, however most thinkpads will be similar. (sweet machine even if that control strip is evil)
My install of Debian is from the Non-Free tree.
Fortunately this is MUCH easier as of this date.
1) start Terminal
2) sudo su
3) apt update
3) apt install xserver-xorg-input-synaptics
To configure Tap To Click
1) Click application menu
2) Settings, Mouse and Touchpad
3) Click the Touchpad link on the Devices page with SynPS/2 Synaptics touchpad selected
4) Click Tap touchpad to click
5) Optionally, select Disable Touchpad While Typing, and move slider down to .5 seconds
6) I also disabled Scrolling Mode