Loose components on the toilet seat, which end up rubbing against each other, are the usual culprits behind a squeaky seat. A squeaky toilet seat goes beyond simply being annoying. Sit on it, and you likely feel it wiggle uneasily underneath you. This easily contributes to toilet users slipping and falling, especially when they rise to stand back up. To remove the squeak, you normally don't need to remove any of the seat hardware, just adjust it.
Put on latex gloves to protect your hands while you work, and lower the toilet seat and lid. Wedge the end of a flat screwdriver underneath the hinge caps on the rear of the toilet seat, and pop the caps open.
Hold the nut that is threaded onto the toilet seat bolt from below, using a pair of pliers. At the same time, twist the head of the bolt clockwise from above, using the screwdriver. Twist the bolt head until the nut fits snugly underneath. Stop, and don't over tighten. Do this on both bolts.
Scoop out a small amount of petroleum jelly on your finger, and work the petroleum jelly into the hinges of the rear of the toilet seat. Snap the hinge caps shut.