The first time we visited New York, in 1999, we stood in line at the TKTS tickets booth in Times Square. It was August, and ridiculously humid, and we stood in the queue for over an hour. Ironically, I don’t even remember what show we ended up seeing (Julie reminded me that it was a pretty mediocre production of Forum) .
As Broadway fans may know, the TKTS booth promises discounted (typically half-price) tickets to same-day shows.
Happily, on more recent trips, we discovered an online resource that offers similar discounts. We paid US $4 for a month’s worth of access to the discount codes database at NYTix.com. They collect and publish a number of discount codes for a bunch of Broadway shows, which you then use when you buy your tickets. The discounts vary, but they’re sometimes as high as 50%.
I assume that lots of these discount codes are available elsewhere on the web. I’m just willing to pay the $4 to have somebody curate, organize and validate them for me. Considering that the TKTS ticket service charge is also $4, it’s money well spent.
The other handy travel trick we discovered is using daily deal sites like Groupon (that’s an affiliate link, by the way–I apparently get $10 in Groupon Bucks if you sign up) in your destination city. You subscribe a few weeks before you’re going to visit, and you get notified of deals that you might want to take advantage of. There’s typically a good portion that would appeal to tourists–restaurants, spas, tourist destinations and so forth. Such sites can also sometimes offer an offbeat activity in a new city. Maybe you’re up for, say, a private salsa dancing lesson while you’re visiting.
I subscribe to Groupon for Vancouver, too, and I’ve found a couple of things I’ve wanted to do. The very first day I bought half-price tickets to the Sustainability Expo, for example.
DarrenBarefoot.com 
There’s another location of TKTS in the downtown area, that is way less busy. I went there on my last trip instead, and waited maybe 10-15 minutes!