Last month, I came across an article by Eve Jacob on how to write magical powers. It was a good read that basically emphasized having a system, limitations, rules that can be understood and broken, etc. I've had a lot of questions from the beta-readers for my upcoming book Gods on the Mountain, regarding specifically the use of magic. Because of this, I thought I would take a moment to explain what role magic plays in the book, and within Calambria (the continent on which my book takes place) at large.
The word "magic" is rarely used in regards to special powers, and when it is, it is almost treated by other characters as a kind of slur. The powers themselves involve a manipulation and utilization of natural elements found within the world. This can include the dirt in the ground, or the flame from a fire, but it can also include clothing or metal armor. This is done by either manipulating the elements from their current state, or channeling those elements through your body. The important part here is that elements cannot be created ex nihilo from the caster themselves - it must already exist. Hence, an adapt user of "magic" must be ready to use whatever is available to them at that moment.
Two things should be kept in mind in regards to this: skill level and physical endurance. A magic user cannot simply do whatever he wants, but rather must harness and focus his skill, in the same manner that a juggler needs to practice to keep up (and advance) his abilities. Likewise, a weak magic user is not going to have enough endurance for what he needs to do, whereas a stronger magic user will be able to cast for long periods of time (and as a result, most magic users tend to be physically fit).
One final, and very important, factor to consider is that, in Calambria, magic and spirituality are connected. Magic is not earned through bloodline, nor through simple training (though training to lower levels is possible); rather, the Almighty (Calambria's monotheistic deity) grants "magic" to whom he wills. It is not inherited, but gifted. The major school of magic in the book, the Order of Magi, recruits by seeking out those who have shown, either at an early age or as a young adult, those who exhibit these powers. Of course, what a person chooses to do with these powers is up to them, and can ostracize them from the magic-using community at large, or grant them greater renown. Those outside the Magi who have exhibited powers for good tend to be seen as saints or holy people, while those who exhibited them for evil were seen as morally corrupt. All of this plays an important factor in the main plot for Gods on the Mountain.