The easiest way to get started with MythTV is to install one of the custom built MythTV distributions onto a dedicated PC.
Many people get started with MythTV start on a low end (usually older) system, then upgrade once they see how well it works. If you have an older 1Ghz or better system you can dedicate to this, that'll probably be plenty.
Start by purchasing a TV Tuner card. Generally I'd suggest a Hauppauge WinTV-PVR-150 since they are very well supported and not too expensive. Some versions of the card do not include a remote, so watch for and be aware of which version you are getting. I'll leave the decision for whether to get a remote up to you.
It's tempting to skimp on the TV tuner card and get a cheaper one to save a couple bucks. Don't. While other cards may be supported, most MythTV users use the Hauppauge PVR series of cards for a good reason. They are a good quality card for a fair price. New users using other cards are asking for trouble.
If you want to output directly to a TV, a GeForce FX 5200 based graphics card is what people on the MythTV mailing list seem to be very happy with. It's a card that does the job perfectly that is not too expensive.
Disk wise, video takes up a lot of space. With my settings, one hour of video takes up 2.2GB. Plan accordingly.
So, now you've got your hardware together, it's time to install software to make the magic happen.
If you are in North America, start by signing up for a Zap2It TV listings account for MythTV, which you will need to setup MythTV. Next it's time to install MythTV itself.
While it's possible to install MythTV on an existing Linux system, there are a lot of version specific dependencies which can complicate things greatly. Although certainly possible, that's not the route I suggest. I suggest starting fresh on a computer using a premade MythTV distribution.
There are two easy to install MythTV distributions I suggest you try. One's not really better than the other, although for certain systems and situations, one may work better than the other...which one that would be depends on your situation.

