You do not need a background in forensics or experience with the CIA in order to identify whether or not your mobile phone has any spyware or not but rather a few resources on the internet and the time and effort to put it into a Google search.
However, the main issue comes from when the spyware has been added and a number of indicators can give it away. Regular errors are one of them. If your phone has become unexpectedly buggy, then this is one indicator.
If the phone’s performance suddenly slows down then that should sound the alarm bells. Not only is that a sure fire way of knowing that there is spyware on the phone but also at the same time, of potential malware and viruses as well.
Another way is to listen to the quality of the call. If there are any clicking sounds or background noise then it could mean that spyware has been installed and is currently running on the phone.
The final way to find out is to search the phone for any unknown files or applications that are hidden around in various files. Depending on the phone and the operating system, go into the system files and folders and search for things that look out of place. Having Google on hand is also a plus and if anything seems fishy or out of place, simply Google it for a full result on what should and should not be there.