If you are sure of your sync frequencies and are using a Redhat compatible distro, Xconfigurator is good. xf86cfg is an alternative if X sessions are available.
I prefer old style xf86config because I feel like I am more in control if the video card is not supported and you need to supply the horizontal and vertical sync frequency.
IF you are NOT sure of your horizontal and vertical sync frequencies, you can calculate them using two display resources.
Using these resources, modlines can be calculated by reference to VESA standards. For my own laptop, the cacluator suggests: Modeline, ("1024x768" 65 10241048 1184 1344 768 771 777 806 -hsync -vsync). This translates into Horizontal sync frequency = 48.36 vertical sync frequency = 60.