DESTDIR in a native distro. How ?

[Ionutz Borcoman <borco@borco-ei.eng.hokudai.ac.jp>]

Hi,

How do I set the DESTDIR in my Makefile ? If a non-debian user will
download the package, he/she will want to install my program in
/usr/local. If he/she is a debian user, the deb package should be
created from the tar.gz and files moved to completely different places,
like /etc, /usr/X11R6 .... 

So which is the best way for solving this ? 

TIA,

Ionutz