Welcome to Gaia! ::

Just write it all out, everything. Then you can cut it down and shorten it if needed. The problem with a long bio is often to keep up the good quality in the text. Yet to have something to cut down you need a lot of text. So write everything down and then trim it. That is how I write novels and such.

Agree with Dokuro on writing it and then cutting it down.

It's nice to have a solid idea in mind for your character's backstory, but make sure to give yourself some wiggle room in case you want to change things up or set up relationships with other characters.

Assuming you are talking about a bio for a roleplay, some important things to note down in a character's bio would be information on how they got to where they are now: information on how they got into a particular organization or school, if that is the setting, or how they became some specific role -- if they are a President, something to show how their dedication or ingenuity put them into that role. Mentioning these things will naturally exude some of your character's personality as well, and they will definitely be interesting to the other roleplayers that are reading it since it is relevant to the setting they are working with.

You can also have a look at the bios for other characters currently signed up for the roleplay you have in mind to join to get a sense of how much you should write.

You are also free to post in the guild any profile write up you have working in progress and we can have a look over it and give you specific pointers for trimming.

Commented on the profile in the thread. Hope it is helpful for you. For future reference, please mention in the profile thread if you would like comments/critique on it -- that way we will know we won't be intruding to post!