Clear your mind of all thoughts. Create a picture in your mind and focus on the outcome you desire. Speak the incantation while continually focusing on the desired outcome.
Some say to meditate before hand, but if you already have attained a permanent clear state of mind free of thoughts I don't find it necessary. Others state to focus on the objective after the spell has been cast instead of during. Some say to focus on gathering energy and visualizing drawing energy into your body to prepare for the spell.
Experiment and find what works for you, for you alone cause the spell to work.