Yup.. we need more information. Did you do anything lately that caused them to stop working?
First check the wiring from the turn signal relay to the hazard switch, there's a purple/orange wire running up there.. make sure it's plugged in all the way. Then check the light blue wire from the turn signal relay to the multifunction switch. Make sure that's engaged with the connector all the way. I recently solved my signals not working by realizing that wire came out of the connector at the multifunction switch after I replaced the heater core.
Lastly, if you don't know if it's been replaced, or haven't replaced the ignition switch yet, it only costs about 20 bucks, and can also be the source of numerous electrical problems, although according to wiring diagrams, the turn signals don't run through there.
The turn signal knob itself as stated above also may be going bad. The little contacts in there get worn out over time. I recently found one on ebay brand new for 22 bucks.
But like I said, check the wiring first, the connectors, etc, before you buy anything.