Rules of Paganism
Guess what... There really aren't any rules!!!  How great is that?!  If it feels right to you, then it's right!  But, one  must always listen to his or her conscience!!
I've mentioned before that I'm not Wiccan.  But the Wiccan Rede is a good rule for us all to follow:

An it harm none, do as ye will.
Wiccans also believe in the 3-Fold Law. 

Whatever you send out will come back to you three-fold.

(Remember the saying, "What goes around comes around"?!?)
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Is it really that simple?  Yes it is.  You'll find some sects that have created strict rules, but most pagans follow their hearts.  But... When dealing with things like "love" spells, you must be careful not to influence the actions and feelings of another person.  The 3-fold law comes into the picture.  So, remember, when casting spells, if it's not something you would want to have done to you, then don't do it!  And, always... You must study what you're doing.  Trial and error is okay for some things, like rune casting, but will spell disaster for some things, like spirit calling.