According the file format, how to know which element should be used?

[ice2000feng]

Hi,
According the file format, how to know which element shoud be used?
for example, I want to play a mp3 file, how to know which source element/convert element/sink element should be used ?
I want to learn GStreamer, but I found the resource about it is very little, I don't know how to learn it better.