Well, for starters, if your character has some inkling their time may be drawing near, I'd suggest a separate thread in the
Private Development Journals section that outlines their Last Will & Testament, if they're the type of character who'd have one. Your character might also choose to discuss ahead of time with a friend or two about who they'd like to handle funeral arangements, especially if your character doesn't otherwise have a written will.
As for RPing that final death... there's not much you yourself can do, since your character will be dead. Hopefully, when your character goes they'll be with a party of good friends and those friends will RP the recovery of your character's body, and the initial scene afterward. One of them may even post a thread to report the death in the RP sections of the forums. You might also make a final CDT entry that describes the scene at the time of your character's death, but be sure to do it in the third person, since obviously your character can't write about it themselves once they're gone.
After all is said and done, I'd suggest also writing up a fairly short bio of your character to be put on display in the
Hall of Heroes and Heroines, especially if their actions through quests or whatnot have left a lasting effect on some aspect of the world of Layonara. Many players don't seem to bother with this option for some reason, which I think is kinda sad. Once these bio's are in-game, they're a great source of flavor and history for new characters to learn about when they visit the in-game Hall of Heroes and Heroines.
Hope this is the kind of information you were looking for and that it helps you.