Hellobee Boards

I usually am, using the same trick you do. They're usually introduced very early on in the episode but they're not the really obvious person--there's always an obvious person that the detectives go after first, and then there's that vague person who actually did it. If there's a "special guest starring" celebrity, they're probably the killer. It's often meant to be "the person you'd last expect", like a neighbor or family member (but not usually the husband or wife since they're the first suspect) or a random person who shows up and seems interested in the case or has a brief interview at the beginning of the episode--which makes them the person I first expect!

Usually; especially with L&O - their red herrings are pretty obvious by now to a loyal L&O watcher!!

The one I had zero clue on was Rosie Larson's killer in the first/second seasons of The Killing. There really were not any clues though in that one; I feel like it was just a big old twist at the end!