There are two parts that might need replacing in the blower motor: the control module and the brushes.
You might suspect the control module when the blower doesn't want to run at all (although there might be other reasons for this as well). Brushes are likely to be worn if the motor doesn't start one day but runs fine on the other. In this case, a moderate whack on the motor from below starts it nicely.
The theoretical solution is plain and simple: lubricate it. In practice, however, this means removing and disassembling the motor (as described in the answer to the previous question)—not something you would want to do every six months or so, wouldn't you? But if you do it once, you can modify it so that you can lubricate it later as often as you feel necessary without going through the hassle of removing it any more.
If it's not working at all, start with checking the fuse #2. Remove the lower shroud of the dashboard (secured by seven screws). A relay is fixed to the right side of the steering column. Turn on the ignition. As you turn the blower speed knob to the full speed position, the relay should click. If it doesn't, check its feed (connector #1). Then jumper its connector #2 to the ground, this time it must click. If it doesn't, it's faulty. If it clicked this time but it didn't when you have just turned the knob to the full speed position, you have to check the heater controls.