how to extract URL of a stream

[anctop]

I have very bad experience when video sites change their ways of streaming, consequently the download tools become useless and, the worst of all, there is no immediate replacement for them.
Therefore I'm eager to learn the method of finding out the URL of a video/audio stream, so that suitable download tools may be chosen.

Download methods for popular sites are widely known. For example, YouTube can be retrieved by some browser add-ons, while RTMPDump is required to get contents from BBC.
However, it is very difficult to dig out for minority sites, e.g. local tv/radio sites.

Intuitively, I tried to read the html source of the page, but the work is hard and fruitless because the true contents are often concealed behind various "players" such that no trace is left in the page source.
I've also heard that sophisticated "packet capturing" softwares are needed for analysis, is that true ? Is there any easier way ?