Eitech's right - avoid looking directly at the oncoming lights, and use your peripheral vision to watch the road until the high beams pass.
Also, something most people neglect to clean is the INSIDE of the windscreen. They wash, polish, and rain-x the outside of the windscreen so it's spotless and water beads off like crazy, but the inside is still dirty and hazy like hell

.
At nite, especially in rain, this haze on the inside reduces your visibility vastly. Take a clean chamois and pass it across the inside of your windscreen and chances are that it'll come off black

.
This is because the interior of your car (vinyls, leather, plastics and rubber, etc) give off gases and vapors and this, coupled with dust that comes in through the windows and off fabrics, creates a haze on the inside of your windows.
Try cleaning the inside of all your car glasses and you'll almost always be guaranteed a crystal clear view out

.