Important steps: recording the base audio, applying effects in layers, previewing each step to avoid overdoing it. Maybe suggesting exporting in different formats to see which one sounds the worst. Also, tips on using online tools for quick effects if they're not into using DAWs.
Maybe include a checklist of effects they can mix and match, and some creative ideas like layering multiple distorted tracks on top of each other. Also, maybe adding some reverse audio or random samples from other sources for a chaotic effect.
Also, adding some humor or messages within the distorted audio. For example, hiding a clear phrase in the noise by using specific frequencies or panning effects. Or maybe creating an audio that starts normal and then gradually gets worse, surprising the friend.
Wait, the user mentioned "best friend," so maybe they want to keep it within a good-natured prank. Maybe suggest setting up a loop of the distorted audio to play on a friend's device or sending it as a voice note. But again, emphasizing the consent aspect.