Here you can see the stitch-selector knobs. The outer (tan) knob pushes in to select A through J, and the inner (cream-colored) knob pulls out to select K through Special. The needle position lever is right of it.
Straight stitch position is AK3. I thought something was wrong with this machine at first, because it wouldn't stitch straight. Turns out, I had the stitch-selectors stuck on some other setting. Thanks to the Yahoo Singer club members for straightening me out!