I don’t know if you could count that as a “tip”, but I definitely advise people to use the original drivers provided by the manufacturer, because they are usually far superior to nouveau. The last time I installed Debian with KDE on my computer it even lagged (I have a GTX 970 + i7-8700K …), probably partially due to my 5 connected monitors. Once I installed the original NVIDIA driver’s newest version, everything runs smoothly.
Additionally, you need to make sure that the driver is actually recognizing each monitor correctly during the X-config creation. If just 1 monitor is falsely added to the list then you have to stay on command line. If someone encounters such an issue, then they should completely purge all X elements (including nouveau) and then freshly install the original driver.
If someone is trying to troubleshoot a display problem, but they keep booting into a black screen, I also advise to add a boot parameter to the GRUB2 entry of the OS. That usually helped me a lot. Here an explanation:
nomodeset
The newest kernels have moved the video mode setting into the kernel. So all the programming of the hardware specific clock rates and registers on the video card happen in the kernel rather than in the X driver when the X server starts… This makes it possible to have high resolution nice looking splash (boot) screens and flicker free transitions from boot splash to login screen. Unfortunately, on some cards this doesnt work properly and you end up with a black screen. Adding the nomodeset parameter instructs the kernel to not load video drivers and use BIOS modes instead until X is loaded.
I also described for beginners how to add the nomodeset parameter temporarily manually here.