There will be a lot of housekeeping that you'll want to do with each of your characters in a number of areas. I ran across a reddit post about what do to after the patch tomorrow with each of your toons, etc. Since it is being updated as more information comes out, I'll share the link.
http://www.reddit.com/r/Guildwars2/comments/22zeof/todo_list_for_april_15th_patch/