After cd'ing into the source directory, do a listing to make sure there is a ./configure. On simpler tarballs, there will be simply a Makefile.
If there isn't a configure file, but there is a config.in or configure.in, then use the 'autoconf' program to create the configure script. I've run into this twice, so it is rare for the packager not to have done it already. You may need to su to root to access the autoconf command. This is also a way to regenerate the configure script if you accidentally deleted it.