I believe whatever you put out there good or bad will come back to you the same way. Funny thing that is though, because you could think that you are doing good, when you are causing harm...So bad will come back to you. Be as specific as you can in a spell. For instance if you do a spell for money, next week Grandma dies and leaves you an inheritance. Instead of asking for money, try asking for say, employment which would equate to money. Another example: You have to have this person be in love with you. You cast a spell and then this person becomes obsessed and stalker-ish. Instead ask for the right person to come into your life...
for me amichai has said it the best, even though she may not say its the simple law of karma, no one said you cannot do anything for your personal gain, but it must not deprive anyone else of their own desire etc
and its very true what you do comes back to you. we will all be "spanked" for wrong deeds and be blessed for right ones.
I personally find when people say "how can we tell what is right" it is an excuse to practice wicked deeds and block out their conscious. eg if i shot a man in cold blooded murder i go to jail, so mundane so magickal.
but commenting to ami's money spell issue, you can ask specifically where your money can come from keeping in mind to remove any negative elements.
"how can we tell what is right"
there is nothing that is right and nothing that is wrong, man has created these false moralities. if you choose to follow them so be it, but not everyone is inclined to believe everything they are told.
I am not saying we should all be able to run the streets, raping killing and stealing from everyone, but theres no place for "right and wrong" in religion and philosophy. The government is intact to enforce the laws of man, the gods are around to enforce the laws of life.
The problem of church and state first came around when governments used Christianity as a way for mass population control...(don't do things we dont want you to do because we dont want to have to stop you.)
if you look at many Christian morals they closely follow the laws of any established government. and when a religion was used to help control people in government, religion itself became tainted with governmental values.
so what I am really trying to say is dont kill people because then everyone else would want to kill people, causing civil disorder wich no one really wants.
don't kill for the government, not karma