Make everything public. As a writer, you should be using sites like Facebook and Twitter to connect with other writers, editors, agents, and your audience. So make it easy for them to find you and learn more about you by making everything available to the public. That said...
Think about your audience, friends, family, boss, former teachers, etc., in everything you do on Facebook. Like it or not, you have to understand that if you are completely public on Facebook (and you should be if you want to connect with your audience) that you need to think about what you do on Facebook before you do it. Because Facebook ain't like Vegas: What happens on Facebook could easily go viral. But don't get paranoid; just use common sense.
Include a profile pic of yourself. Don't use a picture of a cute animal, house pet, your children, an animated character, a famous celebrity, a model, etc. Just a nice pic of yourself. Even though it's virtual, you want your profile to be as human as possible so that you can connect with others.
Update your status regularly. You shouldn't update your status every hour, but once a day is a good pace. This just lets others on Facebook know that you are actively using the site.
Communicate with friends on Facebook. Don't stalk your friends; communicate with them. If you like a friend's status update, comment on it--or at the very least, click the Like button (to acknowledge that you liked their update). Speaking of friends...
Be selective about friends you add. Don't blindly accept every friend request, because some may be bogus, and others may be from serial frienders (people who are trying to hit their friend limits). You want quality friends who share your interests or who you know from the "real world."
Be selective about adding apps. I'm not a huge fan of apps, because they are a distraction and time killer on Facebook. But there are some that could be useful. However, don't waste a month of your life playing Farmville or Mafia Wars; you'd be better off completing a crossword or sudoku puzzle.
Join relevant groups. For writers, there are an abundance of groups you could join, from professional organizations to those based around magazines, publishers and literary events. These are great places to connect with other writers. On that same note...
Follow relevant fan pages. There are many who once had groups that migrated over to using fan pages, so there are fan pages for writing organizations, magazines, publishers, literary events, and more.
As I think about it more, Facebook just seems silly to me. I have a (fairly) regular posting schedule with this blog - some weeks are better than others, but I'm a pretty diligent blogger. I've had this blog since before I've had a Facebook account. Blogging is more satisfying than Facebook status updates. I have better conversations in blog comment threads than on Facebook threads.
I'm just not that much of a Facebooker, and that's okay. I'll still keep my profile. I like having it. But I just can't bring myself to post an update there every single day, because it feels like work and it ultimately distracts me from my writing. I'll focus on maintaining a good blog, and Facebook will be incidental.
However, I was really excited after reading Brewer's bonus tip:
If you have a blog, you can feed your Facebook profile automatically by using the Notes function. All you have to do is go to Notes, click the "Edit import settings" link, and enter your blog url in the correct field. (Note: I had to enter my full url, including the forward slash at the end, before the Notes function accepted my url.)Enthused about a hands-off way to participate in Facebook, I went to my Notes function, tried to import several times . . . and could not get it to work. I tried using my blog URL as well as my RSS feed URL - nothing worked. Even after making sure that I had the forward slash at the end of the URL, I couldn't get it to work. *sigh*
It's not that I'm not optimized for Facebook. It's that Facebook isn't optimized for me.