I have two journals - one online at LiveJournal and one paper one. All of my readings get recorded in both. Well, at least I try to. My online one is a little random. Readings done for me are recorded too. I've been really good about keeping up my written one. I have a very hard time writing a journal just for myself. I journal my life, ramblings, etc. in another LiveJournal. Im the type of person that has to have others read my stuff for me to write it. I can't keep a paper journal of my thoughts, etc. for more than 2 or 3 days.
So my paper tarot journal is rather... systematic. I draw the spread, name the deck, time, date, title of the spread, where I found if its in a book, who/what its referencing/question, if Im reading for/about someone else. I write the meanings of the positions and then what cards I get in those positions. I color in the cards depending on what they are (Swords are orange, Wands are pink, Cups are blue, Pentacles are green and Majors are purple) and underline them with those colors so I can glance over and see the trends.
Then I list the number of the card, the meaning of it, what I got and my interpretations of it, but not too lengthy. At the end I write a conclusion kind of paragraph.