Trojan Horse can come bundled with shareware/freeware or other downloadable software So don't download and try untrustworthy softwares
Always use your Anti-Virus/Anti-Spyware to Scan any Downloaded Software BEFORE Installing. Search for free version from industry standard anti-virus vendors only
Don't be cautious of free Anti-Virus/Anti-Spyware, and DO NOT USE cracked or free serial key for anti-virus program that you may “find” on the Internet. There are free versions from industry trusted anti-virus vendors.
Don't try to find free software/free cracks/free serials/free online games ,etc. through the Internet. Think smart and prevent spyware when browsing the Internet.
Don't visit porn/sexual sites and don't play online lottery/online casino,etc. Because those sites often come with spyware/Adware and various malware
Use an industry standard internet security software such as from: Kaspersky Internet Security/Anti-virus , AVG Internet Security/Anti-virus, Trend-Micro, Norton/Symantec, Microsoft, McAfee, Panda, Sophos, Bullguard, Avast, Avil, ESET etc. (If you are not sure which is the best product for you to buy ask for more information from PC Doctor).
Be aware that most current Trojan Horse arrive as e-mail attachments. Don't open unfamiliar or unsure attachments e-mail
Perform Windows Update Regularly & Make sure that your operating system is up-to-date
Use an industry Standard Firewall (Software/Hardware)