One thing that is super important when starting out investing that I've learned is double check your transactions that you are about to incur. For example during transfers, make sure BTC goes to a BTC wallet. If not, it will hit where it hurts you most, your wallet .
In this example below, Overstock.com wasn't paying attention between their currencies/returns and it cost them a bit. I can only imagine how many people took advantage of this mistake. What do you all think?