Always always set up budget alarms.

Make sure they go to an list with multiple people on it. Make sure someone pays attention to that email list.

It's free and will save your bacon.

I've also had good luck asking for forgiveness. One time I scaled up some servers for an event and left them running for an extra week. I think the damage was in the 4 figures, so not horrendous, but not nothing.

An email to AWS support led to them forgiving a chunk of that bill. Doesn't hurt to ask.