If you're new to this kind of roleplay, it is highly recommended that you read some of the other diaries before you take the plunge, just to get a feel for it. Your entries can be short or long, funny or serious... whatever fits your character.
If you want to date your EverQuest character entries, please observe the EQM time scale HERE
In addition to Diaries, Journals, Logs, and so forth, here are some other things that can go here:
+ "Note to..." Posts
These are temporary posts and will most likely be deleted after it becomes obvious that the recipient of said note has received it. The most common use for this is if the character you are trying to reach does not have an email address. These posts, unlike the posts in "Looking for Group" etc., are 100% in character.
Subject: Note to Doodorf
[Doodorf finds the following note under his pillow:]
Watch your back. I spotted a necromancer lurking around the city gates.
+ Correspondence Posts
These are also in-character "letters," but these are of a more permanent nature. These can be used to carry on an ongoing conversation between two characters who are physically distant from one another in the world. They can also be used to reveal backstory. They are like diaries, in a sense, in that they are for the entertainment and edification of other players as well as the characters involved.
A bard also might carry on a correspondence with a distant sweetheart as he travels about. These allow for a more dynamic type of storytelling than the diaries, as there is another character involved and there is the possibility for the magic C-word... CONFLICT!
Topic line should read something like: The Private Letters of Elerin and Massai.