How do I look up the hsync/vsync values for my monitor?

I'm trying to get my computer to use the correct resolution. For that I need to specify the horizontal and vertical sync values in the configuration file (xorg.conf):

Section "Monitor"  
  Identifier     "Monitor0"  
  VendorName     "Unknown"  
  ModelName      "CRT-0"  
  HorizSync       31.0 - 81.0  
  VertRefresh     56.0 - 76.0  
  Option         "DPMS"  
EndSection

Let's say these values for HorizSync and VertRefresh are somehow wrong for my monitor.
Where do I find the correct values?

Note: This is a "dummy" question -- with the help from the chat, I already found part of the answer, and I am now going to add my own answer to document a solution that is hopefully universal.

Solution 1:

In your monitor's manual.

If it's not there, find out if there are identically built models on the market, or just stick to the default values (they're quite safe and reasonable for almost anything with a VGA connector).

However, before doing it this "hard way", check whether your monitor and video card can't negotiate everything by themselves.

Solution 2:

While I hate the "RTFM or go search Google" answer that was given, it really is best. Go to the manufacturer's site, go to their support section or the place where they offer drivers and software for download, and there will be a place to search for your model. Chances are, they have a link to a PDF manual there. Open it and search for the term Sync. What you are looking for is often called "Synchronization Range" and will likely be under some table with technical specifications.