trouble searching for libs

[Scott Hawley]

Hi, is there a way I can tell autoconf/configure WHERE to look for 
files, e.g. via a LIB_PATHS environment variable?  I've been reading 
documentation and haven't found this info.

What I *REALLY* want to do is, check for the existence of a library 
(somewhere on the disk, as specified by an environment variable like 
LIB_PATHS), and if it's found, then set a -DHAVE_LIB.... one one of 
lines of the Makefile where compiling occurs,  as well as stick a  
-L<dir_where_found> on the linker line.
  It seems to me like this should be a very standard thing to do, but 
I've been unable to find out how to do this either via checking around 
the web, reading man pages, HOWTOs, listserv archives, etc.

Can anyone offer suggestions?
Thanks.
-Scott

P.S. -   When I set, in configure.in,
> AC_CHECK_LIB(mylib,main)
(since AC_HAVE_LIBRARY is now deprecated...), then when I run 
./configure, it says, e.g
> configure: checking for main in -lmylib....no

...I'm confused as to what this is telling me.  I don't see why I 
should be looking for "main" in a library that HAS no main, but that's 
what the docs I read said to do.    Anyway, I think configure is 
failing to look in /usr/local/lib, where I've put my library.