Its a good question. There are a lot of different ways of doing it. In the end it comes down to what possibilities you have and how much money you are prepared to spend. There are several different PVR, or similar to PVR, recording devices that can record anything that passes through it. Even if there are some standard methods every "capper" probably has his/hers own setup and methods. I wouldn't want to go into details here about who uses what...
But in your case, if you would like to make a backup of the shows you are watching for archival purposes wink wink, then I think that for HD and good quality you need to get an external recorder like a PVR or better and record the stream directly that way. For low quality get a screen record program like replay video capture that records exactly what you see and hear but with a slightly lower quality, then watch the show on your computer and record it at the same time.
Usually when you cap or record you set it to the highest quality recording possible and you will end up with a huge file in TS or MPEG format or similar. Normally those files are so huge they are re-encoded to x264 or XviD format and a smaller size. When you have a large source file contact me and ill give you some good hints on what to do with it
