This is not an exhaustive list, but a quick look at some popular shows. For those not listed, I recommend going directly to the network or show web site, and following the links for tickets. General web searches can easily send you to non-official sites that promise you tickets that may or may not be legit - and they will charge you for what should be free. A lot of shows handle ticketing through 1iota.com, so you can also check that out for other available options.
"Saturday Night Live"
Ticket requests are only accepted in August and via email (get full details here). You cannot request a specific date. Tickets are distributed through a lottery system for 8 p.m. rehearsals and the live 11:30 p.m. show. If you don't get advance tickets and are in NYC on a Saturday that has a live show, you can always try the standby line that morning at 7 a.m. at Rockefeller Center. How long that line is depends on the weather and the popularity/newsworthiness of the hosts and musical guests.
"The Tonight Show with Jimmy Fallon"
This is probably the toughest ticket in late night right now, but you still have a better chance of this than getting "Hamilton" tickets. Details here; just make sure you follow their official Twitter account for ticket notices; there are several copycats that look real but are not.
"Late Night with Seth Meyers"
Ticketing through 1iota.com. Of any late show taping I have ever attended, this wins the prize for poshest waiting area. Instead of lining up and waiting on the sidewalk outside, there is a comfy lounge area in 30 Rock where you wait before being taken up to the studio.
"The Late Show with Stephen Colbert"
In my opinion, Stephen Colbert is hilarious, so I had a great time at this week's taping. In addition to the show itself, this is worth checking out just to get a look inside the Ed Sullivan Theater. They do ticketing here, and if you're in NYC this September, it looks like you have a good chance of scoring tickets.
"The Daily Show with Trevor Noah"
I have not been here lately, but went several times when Jon Stewart was still hosting. Go directly to the show's web site for tickets, although they do not show current availability.
"Live with Kelly"
This 9 a.m. show broadcasts from the Live studio on the Upper West Side. Tickets are through 1iota.com. The standby line starts forming before 7 a.m., depending on the popularity of that day's guests.
For all of these shows, same-day standby tickets are released to fill seats of ticket holders who do not show. You'll have to stand on line awhile with no guarantee of a seat, but a lot of people often do get in. For details, check the ticket section of each show's web site.
NBC Studio Tour
If you prefer a tour to a taping, get a look behind the scenes of "Saturday Night Live," "The Tonight Show with Jimmy Fallon," "Late Night with Seth Meyers" and more with the famous NBC Studio Tour. Not surprisingly, you will end the tour in the well-merchandised NBC studio store.
With the exception of SNL, late shows generally tape between 5 p.m. and 7 p.m. Between waiting on line, the audience warm-up and the taping itself, you'll probably be at the studio for about three hours starting around 4 p.m.
If you're more early bird than night owl, you can easily catch a live broadcast of one of the national morning shows. "Today" and "FOX & Friends" have outdoor plazas in midtown Manhattan that can accommodate crowds (Rockefeller Center for "Today," and 48th Street and Sixth Avenue for FOX). Arrive early if it is a concert day. You can request VIP passes here for the "Good Morning America" Times Square Studio, but tickets are not required to see the fun. For these early shows, all you need to do is set the alarm and show up!