If it's folded to me and I'm in position, I bet it. If I'm the early action, I'll either put out a small bet or slowly check, depending on the reads I have on the people acting after me.
Also depends on the board, if my pair is facing and ace on the board, I'm usually ready to toss it. If the board is 10 high and I have a pair of 8's, it's a different hand to me.