I made a reservation 3 months in advance and honestly, it still didn't matter since I wanted a city view table along the windows. My advice, just show up and hit the bar side tables for happy hour and city views.
A couple of ahead
We went last week on a weekday at around 4pm, and it was nearly completely empty...
A day in advance always works for me. Unless as someone pointed, you need a seat by the window.
If you want a seat by a window, you'll need a few weeks advance notice. Otherwise a few days out will work most of the time
A day two ahead is safest except holidays
We went at 4 pm on a Sat. Had a reservation but the place was pretty empty except for the bar.
Thanks! Your answer is awaiting moderation.