Bite sized... lol. Yea, a great way of putting it.
Matthew gave some good ideas of what to do.
Starting hands are a good way to start. One of the first things I would add is ranging your opponent. So you are like "I have xx, and he would call/raise me with what?" So he would call your EP raise with xx range, your MP raise with xx etc. he would raise your EP raise with xx and so on.
Your starting hand range is step one, but preflop, you have to deal with callers and raisers, so you need to fairly quickly deal with this as well.
IMO, it is really ok to be wrong. Just do things because you have decided xxxxxx. In other words, dont just blindly raise, call, fold. Do it because you think xxx. Whatever xxx is. It is better to decide to act because of a wrong reason then to act for no reason.... IMHO.
Bottom line, think about why you do what you do. Then do it. Whether it was a good decision or not, you can tackle later in review.