Make sure your data is automatically backed up daily both on site and remotely.
Utilize Automatic Updates to keep your systems up to date with the latest security patches.
Do not open emails or attachments from people you dont recognize. Do not download files from unknown websites. Utilize www.virustotal.com to scan downloaded files and attachments before you open them.
Do not give out personal information to anyone requesting it via the phone or email. If you must give out personal information, research the company on the Internet and contact them to verify the caller was legitimate.
Install malwarebytes and scan your computer with it weekly or more often. It can be downloaded at www.malwarebytes.com