Frequency scan
As you must tune your DVB card to the right frequency to be able to recieve something, you should better know which frequencies are in use at your place of residence. Note that the used frequencies for North America, Europe and Japan differ, as it always differed and most countries stayd in their old scheme of channels to make a slow switch from analog to digital possible.
The handiest tool for scanning frequencies is "scan" which is part of the LinuxTV dvb-apps; it's especially handy as it uses pre-configured sender lists for many locations, then tunes into the frequencies and lists the names for all available PIDs (for usage, see Scan).
Moreover, if you want to find lists with the typical frequencies, see here (these links are not all great, but here we go):