Linking only required objects

[Bernhard Mogens Ege]

I try to link only required objects into my executable but I dont know 
which objects are required so I add lots of -l<library> to my linker 
stage (using gnu ld). My program is linked and runs. Fine. But checking 
with ldd I see that it now depends on all these libraries, some of them 
I am sure are not required.

How do I find out which libraries are required and which are not required?

Using Linux...

Bernhard