This is where the term CYA comes in. Its always a good idea, but especially so in this kind of environment, to keep a trail of everything. Write emails instead of phone calls, or if you must phone, follow up with a "just to recap our conversation..." email. This way when the poop hits the fan, you can refer back to notes, emails, receipts, etc and back yourself up.
Its also a good idea, in general, but again especially in this kind of environment, to be proactive when yu do mess up. As soon as you notice your own mistake, own up to it, apologize and if you can offer a solution. This way you will have a reputation of not being the kind of person who says "it wasn't me!" so when it really isn't you, and you are presenting your evidence (the CYA trail) people are even more inclined to believe you.