Tip: how I stopped mixing up ので, のに, and から

Something that finally clicked for me at the office (where I actually have to write polite-ish Japanese sometimes): ので and から both give a REASON, but ので is the safer, more formal-sounding choice for work contexts — think of it as the 'business casual' version of から. のに is a completely different job — it's for contrast, not reason, so if you catch yourself translating something as 'because' and it's got のに in it, stop and recheck the sentence, because 'even though' almost always fits better there. Keeping 'reason vs contrast' as the very first filter before anything else has saved me from some awkward emails.