How to unpack maps?

Keep the word "permission" in mind when you feel it necessary.

Before unpacking, make sure the map is not compressed. If it's a map from TF2's Workshop or one that already comes with the game, it's most likely compressed unless it's an official map that hasn't been updated in a few years (3+). Use GCFScape to know that by opening the .BSP file and noticing whether the files (not folders) inside are grayed out AND cannot be extracted. If without compression, proceed to extract whatever you need. If compressed, you can either use the game or the official "BSPZip" tool to decompress a map. This is how:

• Game: I'd suggest you creating a custom folder inside "maps" to put the uncompressed copy of the map in it. Let's suppose you named it "uncompressed". Now, assuming you have the original .BSP file inside the "maps" folder, launch the game, open the console, and submit this command:
  bsp_repack -nocompress maps/mapname.bsp maps/uncompressed/mapname.bsp
• The BSPZip tool: make a copy of the original .BSP file outside the "maps" folder so you don't override it with BSPZip. Let's suppose you have the to-be-decompressed map copy inside "tf"; open your operating system's command prompt, and submit these commands respectively:

1. cd "C:\Program Files (x86)\Steam\steamapps\common\Team Fortress 2\tf"
2. ..\bin\bspzip -repack mapname.bsp

"mapname.bsp" represents the map (or the copy) you're about to decompress.

Apparently not everyone gets my above method to work. I've edited the paths for both the map's Copy File and the command prompt. Hope it works now.