If you're wondering whether to use the words prior to or before, it helps to know that one is from Latin and one is from Anglo Saxon.
Prior to is an acceptable idiom, but when you are tempted to use it, fight the urge. In almost all cases, before is the better choice.
For example, you could say,
Prior to becoming an award-winning clown, Bob was an accountant. (acceptable)
But it’s better to keep it simple and say,
Before becoming an award-winning clown, Bob was an accountant. (better)
If you’ve watched one of my webinars, you may have heard me talk about keeping your language simple and clear by choosing words with Anglo Saxon origins instead of words with Latin origins, and this is one of those cases. Prior to has Latin roots, and before has Anglo Saxon roots—and before sounds more direct.
I actually can’t think of a sentence where you’d have to use prior to instead of before. If you can, please leave a comment.
That’s your quick and dirty tip: If you’re tempted to use the phrase prior to, use the word before instead. It’s not a rule, but it’s a good style choice.