Use temporary credit cards to avoid theft or repeat billing. Most all banks and credit card companies have a way to make a temporary card number, or something like a gift card. Using them will let you avoid a repeat billing you might forget about or risking a high credit limit card if someone gets your card information.
Use a fake birthday for web signups, change your gender, and use disposable email addresses to avoid spam or avoid annoying ads. If you are “male” on a site that is focused on mothering, you are not likely to get breast pump ads. And, having an email address, say from gmail.com, that is only used to sign up at places you otherwise don’t care to hear from, will keep spam corralled to that email address, not your personal or work one.
Use HTTPS whenever possible, create secure, easy-to-remember passwords, and keep your security questions as private as your passwords. On any web login page, make sure you are using SSL or that https:// is at the beginning of the web address. Easy to remember passwords are great but 12345678 isn’t one of them. However frvwtwncrr is easy to remember as it is fairviewtowncrier without the vowels yet rather hard to find in any common list or dictionary of passwords. And, always see if you can make up your own security question or start using your second grade teacher’s name as your mother’s maiden name.
And, some final rules for reigning in software, if you didn’t go looking for it, don’t install it, but, if you install it, always check for updates, and when you no longer need it, remove it.