If you've just downloaded the distribution from the SVN repository, a:

$ autoreconf --install

builds up the building infrastructure (if you want to come back to a "svn
status", go through the ./configure and then 'make extraclean').

If you've downloaded an official distribution, or already you've made the step
before, do a:

$ ./configure
(./configure --help to have a list of pertinent arguments, like --disable-tuntap)

then:

$ make

and if you want:

$ make install


MACOS 10.3:
these extra tools must be installed first:
autoconf-2.59, automake-1.9, libtool-1.5.20
