A. In previous seasons, I've
usually had to hunt down the locations after viewing the episodes,
using clues from the various scenes. By the 6th season, though,
I'd developed a small group of fans, spies & tipsters who kept an
eye out for Dexter filming in their neighborhoods, and would let me know
in advance when something was about to film there.
Between those reports, my own personal reconnaissance around town, and a
few new resources I discovered, by the time the first episode aired, I
already knew most (but not all) of the filming locations, and only
needed to watch the episodes and match up the scenes with the correct
locations.
This group of helpful fans includes Kerry, Rick, Ellen, Susan, Jason, Elaine, Joel, Julie, Geoff, Jeff, and others. My thanks to all of them.
This time, I found it
easily via the scene's background:

As you can see in the screencap above, one of the stores seen behind
Debra and Angel, across the street, has a sign reading "Rock Factory",
in a distinctive font. (Another store nearby had a name that
began with "YOON".)
So I simply Googled for "Rock Factory" and
found it at 5627 Figueroa (near a store named "Yoona"). Once in Highland Park, I knew they
had filmed at the Moda store there for the barber shop scene, so I simply
rotated the StreetView around from the Rock Factory, and sure enough, there was Moda and that narrow parking lot.