If your ultra-paranoid then here is what you need to be on the look out for:

1. massive electricity usage...now I'm talking in the neighborhood of around 3 or 4 x 1000 watt lights and even then it still probably wouldn't raise too many questions by itself alone

2. bad neighborhood....if your trying to do this in a part of town where everyone else does this, then your already on the target list my friend. Many times the police target areas with high crime and or dense pockets of growers like in prelegal California.

3. drive by or fly over thermal camera...this really fits into section 2 as the cops have a budget just like every other organization does and they don't have the resources to fly over everyone's house looking for hot spots. The solution to this potential hazard is to use C3 film or anti-detection film. The infrared cameras cant see your hot spot room if you wrap your room with this film.

4. loose lips sink ships....your own mouth will more times then naught get you into trouble. Don't show anyone including your girlfriends, especially your girlfriends. Don't show your wife if your in the middle of a divorce. These people will have a moral objection more times then naught about what your doing and when the time comes to get even with you, they know this little hobby of yours can land you into trouble so they tell others.

5. smell.......each plant will put off a pretty decent odor after a while. More then a few plants can quickly cause the house to smell if you don't do something to resolve that. Be sure to vent and scrub your grow room air so that your guests and neighbors don't start to ask questions or even recognize the odor.