My biggest tip would be to actually use the portfolio! The home page lists links to them apparently at random (the list is different every time you refresh the page). I clicked on tons of these links the other day, trying to see how others had worded their bios and what info they had included.
I was shocked to see how many people had no more than just their name with out a single article link, accomplishment listed or even contact info!
Another suggestion is to show your personality in your bios while keeping it professional. Many of them rambled on and on in a manner I honestly couldn't see being appealing to potential publishers browsing the profiles.
The ones that stood out the most (in a good way) were the ones that were personable, giving the reader a taste of the writer's personality, while staying focused on the purpose of the page--making the writer look like someone who should be hired!
My last tip would be to update regularly. There were a lot of profiles stating that something would be happening in the future, like in 2004! If it's outdated, it shows that it's not a priority to you to get noticed and get work.
An easy way to remember might be to either update with each new success, like placing in the challenge or being published. If that's not happening very frequently for you right now, then try to update every month or two.