The two main rules for spellcasting are:

The Wiccan Rede
"Bide the Wiccan Rede ye must
In perfect love and perfect trust.
Eight words the Wiccan Rede fufil:
An' it harm none, do what ye will."

The Wiccan Rede states, in effect, that you must not do anything to harm anyone--including yourself. Manipulative magic, doing magic without the object of the spell's knowledge and consent, is considered harm; thereofore, it is outlawed. That includes the "love spells" like were seen in "The Craft". (No--nada--nononono! Is that clear enough?) If that doesn't motivate you to keep your nose clean, how 'bout this one?

The Threefold Law:
That Which You Do, Returns To You Threefold.
That means that if you do manipulative magic or curses, it will backfire and hit you instead of your intended victim. And it will hit you three times as bad. Is that motivation or what?
(As to whether or not the Law of Three exists, last year, I had a lot of trouble with a Fundementalist Christian girl who seized any chance to hurt me. This school year, three months after she had hurt me badly, she had one leg in a cast. I had done nothing that would have caused this effect. She simply, and literally, got what was coming to her. Trust me, it exists.)

Then, there is a major part of magic:
visualization
Visualization is seeing things, sort of in your mind's eye, but in your field of vision. Try this: Close your eyes. Try very hard to "see" something--an object (I tried a snozzberry--you know, from Charlie and the Chocolate Factory). Now, when you can "see" that object well in your mind's eye, mentally take that object and begin to turn it around, studying it from every angle. What does it look like? Does it have bumps, spikes, markings? What is its color? When you can hold that image in your mind for five minutes, open your eyes and try to "see" that object somewhere in the room. Continue to mentally study it, seeing it from all sides and noting every detail. When you can do this for five minutes also, you're ready to move on.
Now, if you've gotten all that, go to my Rituals: The Technical Stuff page. And if you don't understand anything--I mean anything--then tell me. I'll try to explain it. I'd much rather have you ask me about than have you try to do something you don't understand. With magic, always ask questions.