What spells do you have? What itames, if any, do they call for? When did you ty them? Why did you try them. Lastly, wre did you find the spells?
A lot of people say it's better to use a spell you've crafted yourself. I agree with this, as you'll know everything about the spell. Thus, it will be simple for you to cast it.
You also need to know some meditation, as it will help you keep your thoughts focused on you task, while your casting your spell.
Most importently, spells can take time. Not every spell is going to work, but just becase nothing happones right away doesn't mean the spell is fulty. It could be that in a mounth, or in near a year from the time you cast the spell, that is takes effect.
I hope this has helped you some.