The Open Catch Bag
One mistake that is easy to make but should never be made, is to start lobster hunting without checking to make sure that your catch bag is securely closed. There is nothing worse than putting that first keeper into your bag just to see him shoot out the other end and into the murky abyss.
There are a variety of different catch bags, some close with velcro, some with zippers, and others with latches. Whatever is the case be sure that yours is securely fastened.
If you can convince a friend to do it, having a bag man can be very useful. This will increase your mobility and allow you to more easily catch those pesky lobsters. Plus not only do you get to blame him if the lobsters escape but if the ghost lobster happens to appear it will be the guy holding the bag full of lobsters he will be pissed off at, not you.