I was reading the thoughts on weretypes as characters in T&T at the Lone Delver and this caused my to think about it for my self.
I have had one player opt to play a werebear in a long ago campaign and have played a werewolf myself. These characters were both simple shapechangers and so did not require much thought about rules. I have also used traditional weres as villains.
In thinking about were-types one thing to decide early on is what do they change into. It could be a normal animal, a man with animal features (like the Wolfman), or a giant man-animal hybrid. In White Wolf's World of Darkness werewolves pass through no fewer than 5 stages beween amn and giant wolf.
Having decided that, give some thought to vulnerabilities. Are they hurt by normal weapons? Silver, magic, wolvesbane? Does it depend what form they are in?
Do they retain memory and conciousness when they switch forms? In some versions the two forms do not share any memories or knowledge.
How is the change effected? Is it a curse, a disease, as spell, or a Kindred type ability? In some versions of folklore the change is effected by litterally changing skins.
Are these "rules" the same for all were-types? Are there other types of shape-changer in the world?
One of my were-wolf villains was ripped straight from Stephen King's "Cycle of the Werewolf". Luckilly my players had not read it. He was a deranged priest who changed when the moon was full. He shifted into a giant man-wolf hybrid. He could only be hurt by silver or magic when in werewolf form. His index finger was the same length as his middle finger, hair grew on his palms and his eyebrows met in the middle. In his home was a complete abscence of anything made of silver. (I gave lots of clues).
I have also had fun with Selkies who shed their seal skins to walk on land as humans. Anyone finding them could put the skins on and dive in to the ocean as a seal.