Record the things that you do that affect the outcome of the trade and which you can alter. Its not so much about recording the entry and exit prices but what were the reasons for entering and what were the reasons for exiting. How you chose a price for the stop-loss is more important than knowing the stop-loss price in numbers. Knowing the entry pattern and its time-frame is important.
Like with nearly all research, start with the questions you want the information to answer, rather than what information you can collect.