Tonight and tomorrow night mark the last two times you'll be able to capture the soul of Manhattanhenge with your camera until 2013 (unless the Mayans were right, then this will be the last time ever).
This evening will bring the full-sun on the grid, at 8:24 p.m.; and tomorrow night will bring the half-sun on the grid, at 8:25 p.m. You know the drill by now: somehow manage to stand safely in the middle of a street, take photos, send them to us if you want, and don't forget to "oooh" and "ahhh" at our urban Stonehenge.
For more specific advice, look to Neil deGrasse Tyson (who coined the term)—he says: "For best effect, position yourself as far east in Manhattan as possible. But ensure that when you look west across the avenues you can still see New Jersey. Clear cross streets include 14th, 23rd, 34th. 42nd, 57th, and several streets adjacent to them. The Empire State building and the Chrysler building render 34th street and 42nd streets especially striking vistas."