The key areas to consider are:
Your computer or mobile device
Is the operating system (e.g. Windows, Mac OS, Android etc) up-to-date? Is it secured with a firewall, anti-virus and spyware detection software?
Is the browser (e.g. Chrome, Safari, Internet Explorer, Firefox etc) up-to-date? Your supplier will provide free updates - your device might check and download these automatically or you might need to go to their website directly.
Do I recognise the sender? Is it safe to click on this link? If you've secured your device with appropriate software, you should be protected from accidentally downloading something malicious via email. However, because viruses spread by email (sometimes called 'Trojans') are so common, it's best not to open an email you're not expecting or if you don't recognise the sender.
Your internet access
Is your wifi set up correctly? If you use wifi, make sure it's only you using it by setting it up the way the manufacturer recommends for maximum security.
There's a variety of software to choose from. Your operating system and/or broadband company might provide security software free of charge.
Although we can't recommend any specific suppliers, here's a list of a links which you may find useful (in alphabetical order):
If you use Online Services, we recommend you use Trusteer Rapport as an extra layer of protection. It's free to downloand and runs alongside your firewall and anti-virus software.