Alignment on Eventide is generally relative to the plot and theme, not relative to individual to perception. Its purpose is not only to serve as guide for characterization but also an OOC flag of what type of roleplay to expect. No OOC information will ever be known ICly without roleplay, but if you see another character's alignment is "Good" and you are "Evil," you might know to expect a different scene than you would with another "Good" character.
You must pick one of the three categories. If you want to be Neutral/Good or Neutral/Evil, just choose Neutral. Alignment is a guideline, not a hard and fast rule. Good individuals sometimes do bad things and vice versa. Note that also that alignment can change throughout a character's lifetime, just get staff approval before doing so. The next three pages provide a description of each alignment: Good, Neutral, and Evil.
Characters considered Good strive to harm humans as little as possible, but they do not necessarily go out of their way to protect them in everyday life. A Good character, if forced to choose sides in the conflict between the werewolves and hostile vampires, would choose to fight against the hostile vampires. It doesn't have to be because they like the wolves - they might just value human lives and/or the secrecy of their own way of life.
If Good characters are vampires, they may feed only on animals, though this isn't necessary - your character might only feed on criminals or humans with impure intentions. Almost every wolf will be Good (some can be Neutral). Almost all humans will be considered Good, since they have little involvement with the supernatural world. Note that a Good character doesn't have to be nice, and does not have to fit the typical "good guy" ideal.
Many characters will be considered Neutral. A character is Neutral if he or she is not involved in the conflict between the wolves and the hostile vampire clans, and if pushed, would have no desire to choose any side. The character might have slight sympathies with one of the sides, but probably won't act on them often, if at all. It is important to note that characters that aren't in the conflict are NOT automatically Neutral - the character must be truly uninterested in the benefit of either side. A highly independent or narcissistic character might be Neutral, or a character with his or her own agenda. All Volturi members are currently Neutral because they are deemed to have ulterior motives/plans in relation to the conflict.
Neutral vampires usually drink human blood and kill, but they probably won't go out of their way to murder humans senselessly. They will probably be relatively clean with their victims, rarely leaving a trace or suspicion. To Neutral vampires, drinking human blood is a part of a lifestyle. A vampire could also feed only on animals, but vehemently hate and hunt werewolves, or have some sort of darker tendencies. Neutral werewolves may be popular, but neutral shifters (in the Quileute pack) will be rare. Any neutral shifter or wolf will be independent from the pack and might cause humans harm from time to time. Neutral humans are also rare, and would include the Volturi's human companions/servants, or any human that is, for whatever reason, against protecting human life.
Evil characters are almost always vampires, but in rare cases with staff approval, could be human or werewolf. Characters are considered evil if they are human blood drinkers and murders (or somehow harm humans if not vampires). Evil characters want to destroy the werewolves for invading on their lifestyle and harming others of their kind, and they want to put an end to the "Good" vampire lifestyle - they don't believe vampires should have to feed off animal blood.
Many newborn vampires are Evil because they are uncontrolled in their killings and may not know any better. Every Evil character doesn't have to fit the typical "bad guy" profile - be creative and try to explain your character's motivations. An Evil werewolf or shifter would have to kill other wolves and humans, which is unlikely. An Evil human would have to go out of his or her way to kill others and risk sacrificing themselves to align with the vampires.