
First, you should always use your sun visor! Visors are built into modern vehicles for a reason. They can create a comfortable shadow over your eyes, improving your vision on the road. To combat the sun's rays even further, you can invest in polarized sunglasses. They have a special polarizing film that manipulates light waves before they make it to your eye. They can reduce the glare coming off other vehicles.
Finally, it's always a good idea to exercise caution when the sun is in your eyes. Step off the gas a bit to create more room between you and the car in front of you. To ensure that you're seen by oncoming drivers, you can also turn on your headlights.