Re: I'm worried about DD's first tooth...
Not all babies bite, so I woudn't freak out just yet.
When my son bit me, I removed him from the breast and as calmly as possible said "ouch, biting hurts" and made a sad face. I would put him down and let him cry for maybe 10-20 seconds (as long as I could stand it), then return him to the breast. It only took a couple times doing this for him to get the picture.
He did get subconsciously bitey during one bout of teething. He would bite down as he was drifting off to sleep. That time the only thing I could do until the tooth broke through was remove him from the breast as soon as he stopped actively sucking. You can also try giving a cold wash cloth or teething ring to chew on before nursing if you experience teething related biting.
K. Sophia - Mama to my little lactivore, the amazing Mr. X (11/10).