Some stuff is fairly easy to do. I for instance was slapping my ass a lot of for customers when my boyfriend pointed out, that I could easily just clap my hands together. But then I like my ass slapped....
Other PSOs I know keep sound files on their computer for the various popular requests. Farting, sneezing, etc. That is easy to do, but just make sure you know where those files are when you are on the phone! Likewise, online soundboards are great tools for making barnyard noises and the like that are well, often hard to do on demad. I can burp on demand, not fart. Demure I am not, but my ass noise skills are lacking.
For the love of all the Gods and Godesses, I hope you can fake an orgasm--especially you females. Say what you will, but I think you've must have faked it a few times, assuming you're a non-virgin.
Anyway, I personally keep a bunch of soundboards in a bookmark folder just for my PSO work.
Here are a few good ones:
Burps (most of them sound kind of male, if you know of a better burp board, please do share in the comments)
I couldn't find a queef soundboard, but if you're ambitious here's a "how-to queef" video. If anything, it's hilarious: