Be hesitant with your name, address and email address. 
Don't enter this information on a web site until you've read their privacy policy.  If they don't disclose a privacy policy, don't enter any personal information. 

Be secretive with your SSN, mother's maiden name, and credit card numbers. 
These items of personal information are particularly valuable.  Someone with criminal intentions can wreak havoc with your credit record once they learn your SSN and mother's maiden name.  And don't enroll in trial offers if the site insists on having your credit card number.  

Don’t share information with a site that shows no physical location or phone number. 
Look for a street address.  Call their phone number to verify that it's a working number.  If you're still suspicious, send a test email to see if they respond--but don't test this with your real email account.

Opt-out when asked to share your information with third-parties.
If a site's privacy policy gives you the option to allow information sharing, just say no.  You can always go back later and opt-in if you want the site to share your information with others who want to reach you. 

Know your messenger. 
For example, ask your Internet Service Provider (ISP) what precautions they have in place.  If you use an on-line greeting card service, remailer or free e-mail service, be aware that you are providing your email address and that of the addressee. Are you using a public facility for entering or transfering data? Transactions with any third-party inherits risk.

Don't talk to strangers. 
News groups, bulletin boards and Chat rooms are not secure.  Email from you tells recipients your address. Consider using a third-party such as ZeroKnowledge  to email and do other transactions anonymously.  Or, consider using a third-party remailer such as the Anonymizer.  Such third-parties might not be perfect, but helpful.  Consider using more than one e-mail account; perhaps one at a Community Access Center. But, in all cases, remember to Know your messenger. Even if off-line be careful not to give out information that can be joined with on-line information --- like having your Social Security Number in a public file or giving out your address over the phone or giving your mother's real madien name. Beware of any stranger appealing to your sympathy, fear, sense of duty, vanity, laziness, lust, guilt or greed.

Turn the tables.
Consider putting an extra word or character in your postal address.   If anyone else contacts you using that information, you'll know who's been sharing your personal information.

Don't leave entrances open.
Close every password protected program and all associated windows or shut-down the computer before walking away. Consider password protecting access to system resources with a screen saver or with a system start-up log-in prompt.

Take care with your keys. 
Your password is the key to your accounts.  Don't trust people with it.  Unlike your house key, change it often, at least monthly. As best you can, sheild your hand if entering the password at a public place. To make it hard to guess, don't make it a real word, phrase, or number sequence. Use odd characters and upper and lower case letters.  Longer is better than shorter.  Hide a copy well; not under the doormat. Having different passwords at different sites is a best practice. Specialty programs like InfoKeep can help. IE5 has automatic password management.  On-line services are emerging such as Passport. If you want to use a memory trick, take care that it uses randomness such as: take a photo album, hold it upside-down and see what keyboard characters the pictures suggest to you. 

Limit physical access by others.
For example, does the nightly cleaning crew have access to your media, machine or memos?  How about the folks who take care of the office plants?

Don't accept food from strangers.
Cookies can be a delightful treat to you from sites, enabling sites to store on your hard disk the information you want sites to have so that each visit to the site will have your preference remembered.  However, like any treat, in the wrong hands, it can be used maliciously by the unscrupulous to store information that you would rather they not store.  Dumb cookie ingredients:  where, what, when, and how often. It can only be a smart cookie if you provide the information. You are in control !!! You can block all cookies using browser settings; you can opt-out from receiving cookies from specific site advertisers such as DoubleClick; you can manage cookies with programs such as Opera; and, you can delete cookies from your hard drive --- manually or with your browser's assistance. 

Don't allow eavesdroppers.
SSL browsers and S/MIME email programs can scramble messages; only the proper receiver can unscramble the message. That's cryptography, i.e. encryption encodes messages and decryption decodes them.  But, often encryption is used to mean both encoding and decoding as a process.

Require positive identification.
SSL (Secure Socket Layer) browsers and S/MIME (Secure Multipurpose Internet Mail Extensions) email programs insure the receiver is not an imposter. They perform authentication by demanding a certificate issued to the site by a Certification Authority  (CA) such as Equifax , GlobalSign , and VeriSign .  They also validate the integrity of messages received.

Update your browser version. 
Get the most recent version possible to obtain the latest security technology.  Look for encryption features in the browser you choose.  A program with this feature will display it proudly.  128-bit encryption is better than 40-bit encryption.   

Use a browser that supports SET or SSL encryption.
Secure Electronic Transfer (SET) is a set of rules (protocol) for encrypted transfer of credit information over the internet. Secure Socket Layer (SSL) is a protocol for secure sessions over the internet. 

Use tools from trusted sources.
Leading programs are from well known companies.  When new programs come along, check out the program's development company.  For example,  do they have a write-up in a credible magazine?  Whether buying, borrowing or downloading, obtain your program from a reputable source.  Try Netscape or Microsoft  (Outlook Express comes free with Win9x/2000) .  You can often verify features and performance in trade publications such as ZdNet , PCWorld, and Public Broadcasting Service.