To be honest with everyone, the posting of my "Lost Caverns of Tsojcanth" campaign adventure progress is actually the first time that I have ever done anything on the lines of keeping a journal. I started it because there were a couple of other site members that asked if I could since they would not be able to join in on the game due to distance factors. It has also helped for when a particular player wasn't able to make a game session, they were able to know what took place while they were away. Another advantage to having a campaign log is that if you find that your group has to bring a new player into the ranks, this does allow for the new person to be able to know what has happened and hopefully be able to step right in and start playing without having to be told all this at the first game session that they are at.
To be able to make a good naration, I take notes of the major points of the session so as to be sure and not miss anything. The same notes also come in handy for awarding the experience points for other than just killing monsters and such.
I look at the campaign log as being a story. You want to try to make it seem like a good book so that the reader will be interested and want to keep following it. I have found that it seems to keep it simple by just making entries grouped by each game session. Now I will be the first to admit that I am not like a professional writer in any way, but I have found that it is really not that hard to make a campaign log. Sometimes the real challenge is just trying to find the time to actually type up the entry.
For some examples and to see different styles of writting, there are a couple of campaign logs on some of the members blogs here on the site. Pop over and check them out, for they are all a good read.