How can you tell if a building is on leased land?

Yep, the financial terms of the lease (land lease payment, lease expiration, etc.) will be in the building's financial statement. You can also call the managing agent or check the offering plan (although it may not be updated.) The most recent financial statement will have the updated info. Hope that helps.

I bet the info's on ACRIS, but I don't know which specific document to check.
Anyone?

I was wondering if there is a way to check very early in the process because frankly I am not interested in even looking at these properties. The Excelsior (303 East 57th Street) is one such example with huge apartments but outrageous maintenance just waiting to get worse. Yesterday a broker took us a to see a place on East 62nd and when I looked it up on Streeteasy, I happened to notice a discussion related to it indicating that it's a land lease. The broker never mentioned it.

lo888...I think the thread you meant to start was:
My broker is either totally incompetent or a complete sleaze bag

I'd find another one if I were you or, if not, tell them you don't want to see any land lease buildings. And tell them in writing.