A disclaimer before we get into it: this solution is really just bringing the numbers on the oven dial into alignment with the temperature inside the oven. We're not actually adjusting any of the inner workings of the oven itself. If your oven temperature is off by more than 100° or fluctuates a lot in temperature, you'll need to call a professional.
First, check the thermostat sensor bulb at the back of the oven. It should look something like this:
Next, remove the oven temperature knob and take a look at the back. If it looks like this:
If your knob doesn't look like this, then the alignment mechanism is probably in the shaft of the knob. Use a screwdriver and turn it clock-wise if your oven is running hot (to lower the temperature) or turn it counter-clockwise if your oven is running cool (to raise the temperature).
Again, this fix isn't actually adjusting the temperature sensor or any of the oven's heating mechanisms. Call a repair person if you think something is off with either of those things.
Related: Our Adventures in Oven Cleaning
(Images: Emma Christensen for the Kitchn)