This depends greatly on whether I'm writing fiction or non-fiction, and even then why I'm writing if non-fiction.
With fiction it's really difficult to not add myself in - extremely difficult. I'd go as far as using the word impossible. When I create characters, they are all a part of me. They had to come from somewhere, and if that's somewhere is my imagination, then there are bits of me strewn through a manuscript like that glitter you can't get out of a couch after a kid's party. There are bits of my family, bits of people I've met, bits of people I've worked with, gone out with...
And, of course, there is something to that old saying that a writer will "write what they know."
Of course I'm in my writing. I wrote it, didn't I?
In non-fiction, however, that's a different kettle of beans.
If it's an opinion piece or Rick Mercer style rant, then there is quite a bit of me. Actually, it is all me. Unedited and uncut and on a roll.
However, if I'm writing a piece that requires research and objectivity, I have to remove myself (and what bias I have) out of the picture and concentrate on facts and presenting them logically and concisely. Information is being passed along and it's not right for it to be filtered through a lens coloured by bias.