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Don’t use lazy passwords. Choosing password or 1234 is like putting a luggage lock on the front door of your house. Also, people will be able to guess it and hack. Instead, come up with a longer password that contains both letters and numbers/characters, preferably one that references something significant only to you. For example, if the name of your beloved childhood goldfish was Sir Bubbles, swap out some of the letters for numbers and you can end up with a very nice password like s1rbubb735 that only you understand. Make sure to write all of your passwords down as well.
Never use the same password for different accounts. If you don’t want to come up with and keep track of dozens of different passwords, come up with a base password (ex. s1rbubb735) and tack a logical modifier onto it for each account (ex. on Amazon, use amzns1rbubb735; on Gmail, use gmails1rbubb735 or for Twitter twitt1rubb735).
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When signing up for / installing / agreeing to anything, read the fine print. If you do not want to receive junk mail or get put on a telemarketer list, look for a small box near the bottom of the page that asks if you want to receive information and offers from other companies. The best sites will have a statement listed that they will not sell your name to other companies (though they may still spam you themselves). Some sites require you to give all your information to get the product. Only fill in required fields that are marked with an *. If the info box does not have an asterisk, it is optional and you can leave it blank.
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Do not give out your full name, address, or phone number to anyone online that you don't trust or know in person. This especially important in chatrooms or when negotiating jobs or deals through meet-up sites. Beware of stock letters (i.e. very general response letters that don’t actually address any of the points you’ve made), anyone who wants to negotiate a wire transfer, or anyone who wants to work out a business arrangement while they’re “abroad.” Read How to Avoid Scams on Craigslist and How to Avoid Internet Dating Scams for more details.
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Keep your eyes peeled for online scams. Beware of spoof email claiming to be from eBay, PayPal, or a bank or a company you trust asking for personal or sensitive information. This is called phishing. The e-mail may inform you that there is a problem with your account/password. There may be a link to click inside. Forward any of these e-mails to the company it claims to be sent from. They will confirm whether the e-mail you received was real or not. Also, bear in mind that e-mail programs like Yahoo!, MSN, Hotmail and Gmail will never ask you for your e-mail password. Don't fall for it. Read How to Protect Yourself from Phishing Scams for more information.