disclaimer: nothing I say is true. make this assumption before reading anything.
The first type I'll refer to as 'impersonal'. This is the paranoia where one thinks that there are a lot of people out to get people, and could in certain context be considered an awareness of repression. "The government is trying to rip civil rights away from people" is an example.
The second type I'll refer to as 'irrational'. This is the paranoid that thinks the entire universe is plotting against him. I've always thought that this was supremely arrogant that the world would care that much. This, I've noticed, sometimes evolves into a self-fulfilling prophecy. If you rant long enough, people will start to talk about you. If you are obsessed with your impending doom, you may be creating it. The 'irrational' paranoia will lead you to be unhappy.
The third type is the 'rational' paranoia. This is the healthy kind. I also like to refer to this as 'being cautious'.
I'm going to direct this to hackers, phreakers, pirates, and any other breaking the law. You are breaking the law. The government, may, if they knew, try to 'get you'. It makes sense to prevent this.
Many years ago, I was talking to Mind Rape on the phone, and he said (I'll paraphrase) "they're all out to get me, they're tapping my phone, they're watching my every move". He turned out to be correct, I thought he was wrong at the time, but being right was useless - he still got busted.
Don't write things down. Little scraps of paper is probably the reason it takes the government 4 years to prosecute a person after they've been raided. But they do prosecute. Think of your output in terms of 'evidence'. Try to create as little of it as possible.
This includes a notebook! How to operate away from your house? Make a printout and burn it when your done. Realize that cops can trash just as easily as we can.
Gail Thackery and her ilk love our tradition of having a notebook that's rich in diverse information. Don't make their jobs any easier than you have to.
Use encryption. Encrypt everything. Make it easy (so you do it!), but don't compromise your security. Using all the encryption in the world doesn't help if you have a 'bust-me notebook'.
If people you know get busted, lay low for awhile. Be aware that the police probably have your number if he called you direct.
You shouldn't have to 'clean house', or go on an evidence destroying purge, because you shouldn't generate much evidence. System logs should be considered evidence as well.
If you have reason to believe you are going to be busted move your system elsewhere. Store your encrypted data someplace very safe (not where the system is located). When loaning out your computer, wipe (and government standard wipe!) your drive free of all data. Norton has a good wipe utility.
If you do most of your hacking from your own account, there's nothing I can say to make you smarter. Ditto with the home phone and phreaking.
Know the laws. Don't rely on hacker folklore. No matter how long your "really, I'm not a fed" BBS application is it won't protect you. It may in fact call attention to you, or confirm your illegal intents. Read the laws. Go to resources that are somewhat reliable. Don't expect your case to be a cause.
Know what crimes your committing. Know the penalties. Know the jurisdiction (it could be FBI, SS, Local, State, or international authorities).
If you can, know the policies of your victims. For instance many people won't pirate Novell because their Draconian against BBS's who carry their warez. Many companies won't prosecute hackers because of their image. Many or most law enforcement investigations start out because a company files a complain. If they refuse to file complaints then they are much safer to penetrate.
Note that many corporate security officials have close ties with law enforcement. One day after a friendly informational interview with Microsoft Piracy investigator I received an email from a friend of Gail Thackery telling me to call her. This is a 'web' of enforcement, coordinated in many cases. Be aware of this, don't write off the person whose job it may be to find you. You don't ever want that attention, best if they never knew you were there.
There is a risk to everything we do in life. This is often part of the reasons we do it. Don't be scared, be informed and cautious, and hack, phreak, or pirate free from paranoia.