create or edit short cut entry in Gnome, Thunar etc

1) create a file app-name.desktop

2) edit app-name.desktop file , to have the following entries

[Desktop Entry]
Version=1.0
Encoding=UTF-8
Name=GIMP
Exec=gimp (command to be executed)
Tcon= location of the icon file
Type=Application


NB:- tested on ubuntu 9.04