Modification takes many different paths, allowing its users to change their bodies in a myriad of ways. The types of changes a Modifier can make are only limited by the imagination.
Some Modifiers, particularly those of the Vitra Phase, use their Gift to enhance their bodies for battle purposes. They can grow claws and fangs even while in human form, or can change the size of these weapons while shapeshifted (one of the easiest changes to be made). Others can grow additional parts to their bodies, such as ankle spurs or spine ridges, or even horns.
A semi-variation of most combat modifications, some Modifiers can control their Shifting, and learn to "partially" shift. Not only can these individuals grow claws and fangs, but they may be able to control the Shift to their other forms, and guide or even halt the process at a certain stage. The most famous usage of Modification in this way is a human-form, with a wolf (or, to be more precise, Fireblooded) head. This is a top level ability for Modification.
Some choose to change their size, either larger or smaller. Umbra have been known to use this ability for stealth purposes. Extremes of this change are some of the most difficult, as even werewolves tend to follow the laws of physics, and while they can bend the law of Conservation of Matter some by their very nature, it still requires great will to be able to force an extreme shift of mass. No Modifier has ever been able to grow larger than 150% of their regular mass, or smaller than 50%, however.
The other change that is accomplished with great ease, but is far more cosmetic, is the changing of colour. Hair colour, eye colour, tattoos, and sections of fur colour. Another simple change is the creation of piercings. Some Modifiers use their abilities to be able to maintain piercings even while in wolf form. Some other slightly-more difficult changes, but still relatively easy, involve changing hair length, and minor physical features. No, it is not uncommon for a Modifier to "fluff" their 'assets', as it were. Both genders.
Other cosmetic changes take more skill and power, but can be just as useful. They can change their skin colour, their features, and even body types. Extremely gifted cosmetic shapers, usually known to be Umbra, are capable of shifting their bodies to completely take on the appearance of another person.
The rarest, and most difficult use of Modification, is to change one's biological sex. It is an extremely narrow subdivision of cosmetic changes that requires much practice, willpower, and a fair amount of knowledge to pull off successfully.
Most werewolves who attempt this will only make surface changes. While they may go so far as to change their genitals, they will still have the reproductive functions of their original sex; most who are capable of this level of change do manage to consider urination.
A truly educated and skilled master can even change their internal reproductive organs, and will consider something as minute as hormone changes in the body, changing the size and shape of the voice box, etc.
It is extremely difficult, and most werewolves don't even attempt it, because they are so entrenched in their own body image and gender role.
Generally, the changes made are relatively simple in thought and work. It is not much to change colour, or the size of a single relative body feature. Changing entire body size is usually easier than changing proportions, because the individual need only think about their body as a whole and for the most part, the change will happen. In general, it is easier to modify what exists than to create something else. Turning fingernails into claws is easier than growing horns.
Changes to internal workings, particularly those where the effects are not visible, takes extreme concentration and knowledge of what is being changed.
One of the first problems that Modifiers will run into is the energy required to power their changes. Some may transform their body, and find that they do not have the energy or focus to change back to normal. Some may find that they do not have the energy or focus to keep the changes. The style of maintenance depends on the individual.
A powerful Modifier that does not know what they are doing or lacks focus may overextend the modifications that they are making. It is no fun to deal with a mouthful of teeth that don't fit comfortably inside your jaws anymore. Ripping open your skin as you grow bone spurs or claws because you didn't think to change the skin around them is no fun either. Modification does not translate into a higher healing rate.
Size changers also have to think about their entire bodies as they change, or the entirety of the affect parts. Those who grow larger may find their skin stretching and attempting to tear if they do not think to include the skin in the growth.
Those who wish to learn more to further their Modification often study medical fields, with intense focus on anatomy and physiology. The more a Modifier knows about how their body works, the easier they are able to change it.