Get the Whitepaper called Anti-Virus Evasion Techniques. Some of the techniques discussed are binding and splitting, converting exe to executable client side scripts, and performing code obfuscation/morphing.
You can download it from the following link: https://packetstormsecurity.com/files/download/107770/avevasion-techniques.pdf
Source: https://packetstormsecurity.com/files/107770/Anti-Virus-Evasion-Techniques.html