shared library loader configuration

[no at spam at mgedv.net]

hi,

can someone give me please a SIMPLE and CLEAR answer,
what i exactly have to do to achieve the following:

i have (for example) installed a new compiled version
of libz.a/.so in /usr/local.

i want program (during runtime AND during compilation)
to compile and run against the NEW and non-system libs.

what has to be set/changed, to have this setting as soon
as the OS starts?

i tried running ldconfig, i was playing around with some
ld-so.conf files, everything failed. the compilation does
not even find the new libraries, and if i use "ldd" to
check what path the lib would use it's always /lib or
/usr/lib instead of /usr/local/lib.

please don't tell me things about RTFM or weblinks, i just
need ~3 simple lines of what the hell to do that i get
a persisting setting for compilations and runtimes, which
i don't have to e.g. export everytime i want it to work
(talking 'bout LD_LIBRARY_PATH or CFLAGS/LDFLAGS). this
cannot be a good solution, as soon as i start with a clean
environment, there has to be a way to tell the os, MAN load
it from there first!

many thx in advance for not flaming me & telling me how's
it meant to be ;-)