When choosing a new VA, I've given 1 or 2 basic tasks a brain-dead monkey could probably do. Too easy. Gotta give them something more complex to separate the A-team from the B-team.
VAs aren't stupid, but they're not high IQ either. Too many times I've assumed my VAs understand what I need when really they had no idea. They tend to be kind of timid so they might not ask for clarification before doing it the wrong way.
This is probably my biggest mistake. VAs are extremely valuable, but you have to train them correctly. They'll do what you need them to, but only if you are VERY specific in your directions. Leave no stone unturned.
All a learning experience.
Side note: Where I find my VAs is onlinejobs.ph