Physical Appearance
Three traits are said to define powerful witches:
+Red hair
+Green eyes
+A sixth finger
Though not all powerful witches exhibit these traits, only the powerful can carry them. One trait is said to be mainstream material, two traits is to be feared, all three is a mark of godly power that has only been seen in two witches to date, Deborah and Antha Evelyn Mayfair.
Abilities
All witches have a sixth sense, however slight, and the more powerful can have a number of abilities that are used by their minds in conjunction with spirits (telekinesis, astral projection, mind reading, premonition, etc.).
Around Vampires
Witches can tell vampires on sight and have a natural fear or hatred of them. Most just run. Others continue on like normal. Some of the less sensible approach them and attempt some form of contact. However, some witches have the 'fire gift', the ability to summon flames from the air and direct them anywhere they choose. This will always, under any circumstance, kill a vampire if it makes contact.
Around Werewolves
Witches do not hate werewolves the way they hate vampires. They have no history together, so the slate is clean. However, many find the lifestyles and very nature of the werewolves revolting and so they look down upon them. A few take them only as a threat. Overall, a witch's reaction to a werewolf varies greatly from person to person.