1. Curses cause a state of mourning, G-d forbid.
2. One does not have permission to curse unless he can see the generations to come from the one [he is cursing].
3. Do not take the curse of a common man lightly (in your eyes).
4. Curses affect according to the intention (with which they are said).
5. Sometimes the curse of a tzaddik are fulfilled as long as he lives, but not after his passing.
6. In the end, an unjustified curse returns upon the one who cursed.
7. The curse of a Torah sage comes to pass, even if it was unjustified, and even if it was given conditionally.
8. Even a non-Jew who blesses the Jewish People is blessed.