Well I see nothing wrong with handing someone a loaded gun lol. [Please don't go around cursing people, I'm responding for educational purposes only]
If you know how to cast a spell you can cast a curse. With a spell you charge energy, focus and visualize your desired outcome. You should also focus on the positive, if it's a love spell focus on that warm feeling, if it's money think of all the good it can do. With curses, you focus on your anger, rage, and negative feelings towards the person. Instead of building energy [you do charge energy in a curse] you build up all your negative emotions and direct them at the target.
You can also curse yourself so be careful. When you cast spells energy builds up in your home and body [which is why regular cleansings is wise] But this energy is usually positive. When you cast curses, you're focusing negative energies, this can build and bring bad things your way. You may not break your arm because you cast a curse, but that negative energy will weigh you down, make you miserable, and feel terrible. Granted, one curse won't turn you into a ball of misery, but if you focus on a bad situation, you will be in a bad mood. This can build, so don't curse someone unless it's an absolute last resort.