If you have a TV Card with MPEG Hardware Encoding, then you should check this topic : Tips For For Mpeg Hardware Encoding Tv Cards - Image Quality and Sound Settings (if LivePreview Mode is not enabled).
Now about some additional tuning :
- Set Preview Format to 768x576 (or 640x480) and enable overlay mixer - use ChrisTV Quick Config Panel for that ( ChrisTV.exe /config )
- Enable Dscaler Deinterlace Filter (download it first from http://www.chris-tv.com/download.html )
- Adjust the Sharpness Level of the picture, by going to Program Settings->Image & Sound Settings.
-If you have unwanted lines (black and white dots) on the top or bottom of some channels use the Zoom Function to get rid of them : set the zoom to 1-3% and to the center of the image.
Also make sure you have the latest WHQL drivers for your Graphic Card :
- For NVidia Graphic Card Drivers visit this page : http://www.nvidia.com/content/drivers/drivers.asp
- For ATI Graphic Card Drivers visit this page :http://www.ati.com/support/driver.html
Some settings for the Deinterlace Filter in ChrisTV :
Deinterlace Type : Dscaler Plugin
Dscaler Plugin : DI_GreedyH.dll
(enable/disable : Is old field first option )
For more information about Deinterlace filters check this topic :
http://forum.chris-tv.com/index.pl=deinterlace

Why does Dscaler have a better image quality ?
Dscaler works with it's own drivers and is working directly with the hardware, so you can end with your TV Card "burned" if there are some bugs in their drivers.ChrisTV works only on TV Cards with WDM/BDA Drivers - the one supplied by the TV Card manufacturer or any other WDM/BDA generic driver.
You can try the btwincap wdm generic driver ONLY for TV Cards with BT8x8 chipset which might give better results (check if your card is supported by it) - http://www.chris-tv.com/links.html.

Added in ChrisTv 3.80 :
NEW option "Use Advanced Rendering Mode" to improve the image quality on TV Cards that have only the capture pin (like Asus TV/FM and Combo Cards)