You don't tell
Just because they ask, you don't have to tell. If you are just setting up an email account, you don't need to have a comprehensive profile.
And if you are joining a social network, you can limit the amount of personal info you give out to the minimum.
You can always make up an email address if you do not need a reply.
Cookies are Best when
You can eat them
Make sure only the websites you visit will be able to collect information in the form of cookies by setting your browser to reject third party cookies.
This way you can reduce the chances of the info being stolen by unscrupulous trackers, for example, via false adverts embedded on websites you visit.
Make sure your passwords keep your data safe and are not passports into your personal details.
Don't use the same password everywhere, don't use a username on one site as a password for another. Hackers can cross-reference. Do use numbers and letters, some in capitals, in combinations that are not dictionary words.
You give it away
For others to sell it
Dig a little and take a look at other people's profiles - what you can read about them, others can read about you.
Posting pictures can also mean trouble. Once you've put your personal photos online you have very little control over how they are used. Still want to fill in all those details?
Keep your personal data
Under lock and key
Social networking sites are a goldmine for data-harvesters, so make things tough for them by setting your profile to the strictest privacy options.
In a heated debate you may let slip more than you realise, so check what you are posting to make sure no personal details have slipped through.
Close one door before
you open the next
Leaving yourself logged in to a social network or bank account is like leaving your car unlocked: you are wide open to infiltration by hackers. So avoid the risk and log out of accounts before surfing.
Who's hitching a ride
on your network
If you are using a WiFi network make sure you don't have any hitchhikers along for the ride.
Secure your network with a robust password and where possible use WPA encryption as this is stronger.
It's a two way street
You keep your computer safe, you pay attention to your online details, but what about the people who are storing your info?
You may have selected the highest security settings, but if a site can't keep your info safe, then you are still vulnerable. How trustworthy are the site owners and their own security systems?
Consider using a payment method that is just for online shopping. Set a low credit limit: then if someone does get your card details, there's only so much damage they can do.
The large print
giveth and the small
print taketh away
As true online as it is elsewhere, make sure you know what you are signing up to.
For example, some contracts are auto renew and you have to opt out at a certain time if you don't want your credit card to be debited.