Growing some freedom
My definition of Free Will is: the ability to determine the options available to you and the ability to make a choice amongst those options based on your personal wants and needs.
Given that definition, you can improve your Free Will by seeking knowledge and by thinking and behaving morally.
I'm NOT saying that there is such a thing as "absolute" morality, only that thinking about the morality of your actions will make you see options differently and will give you a better ability to make choices, and so it will increase the "freedom" of your will. In fact, making the assumption that there is an absolute morality will undermine the gain in freedom that moral reasoning would give you otherwise.