I would start at the high beam switch. With the headlights on, cycle the high beam switch a couple dozen times. If you get any light at all, even just a flicker, replace the switch.
Next break out the test light (or meter) and check for power at the 3 wires on the high beam switch. Two of the three wires should have power in either position (One in, alternate of the other two going out).
Nothing at all getting to the high beam switch? Check the headlamp switch itself.
Everything happy at the high beam switch? Check for power at the bulbs.
The high beam switch is a common failure point and also cuts the trouble shooting for the other parts in half. So that is where to start.
