Here are the things to look out for:
Bushy Joined Eyebrows
Unibrows are normal. Especially when your hormones tell that you are hairy. But if the brows are really thick, grows in every direction, and looks odd or scary, there might be another reason.
Small Pointed Ears
Check the ears. Do they seem normal but look something like “hobbit ears” as seen from The Lord of the Rings trilogy?Ring Finger As Long As Middle Finger
Normally, each of our fingers differs in length. But another sign to suspect is when the ring finger and the middle finger are as long as the other. Try to check yours now.
Hairy Palms
As we can observe, the skin on the soles of our feet and the palms of our hands differ from the rest of our body. That's why we cannot see any hair growing. I think this is the best way to detect, among the others presented, because of the rarity of the case.
This is just based from what they call superstitious features of suspected werewolves in the old times. We don't know if the clues are true or are they still applicable in this day and age. Everything depends on the person's belief and it is up to you if you believe or not.