When I put custom sounds/music/quotes etc. in a map, do I put them also in the ZIP folder along with the map?

I think that there is a way to package them into the bsp itself. I think it is called Potato Packer.
It is on this website.

Custom sounds you can directly pack into the .bsp using pakrat (or any other .bsp content packer). If you really wanted to you could put the custom sounds into a .vpk (using the console application in your portal/bin folder) instead of packing them into the .bsp however this will install the sounds into the player's directory.

You can get pakrat here: http://www.bagthorpe.org/bob/cofrdrbob/pakrat.html
Here is a good tutorial on making VPK's: http://developer.valvesoftware.com/wiki ... d_shipping

Thanks for the info. I found a few spooky unused GLaDOS quotes that I'm going to use for my horror themed map pack.

For completeness: VPK tutorial for Portal 2: http://developer.valvesoftware.com/wiki ... rtal_2_Map

A thread I initiated a few weeks ago might be of interest regarding this (link).

Long story short, if you include custom sounds in a VPK the user needs to update their audio cache, which isn't necessary if the sounds are embedded in the BSP. There also doesn't seem to be way to get VCDs and custom soundscripts to work with a map you plan to distribute (i.e., only raw sounds will work), but I don't think that's relevant to your question here.

Even if it isn't relevant, it's still good info. Thanks anyway.