Using a second HD and installing apps on external drive? I am considering adding an extra drive to my Mac Mini (possibly a tower-size one like mentioned here) and keeping it permanently plugged-in, for extra space and to leave the main Macintosh HD for essential files - system apps, my Adobe apps etc.

I have a 500GB hard drive, with currently 204.68GB remaining on it, but was considering using the additional drive for the other files I create. I also have a portable drive (SATA) which is NTFS-formatted, but that's used for files I frequently need to carry around - PowerPoint presentations etc.
On the additional hard drive, it would be for other things that are less frequently used.

However, what would be the best way to go about this? Also, do applications work well if installed on an external drive - e.g. Quark XPress, MAMP etc. (although I may leave MAMP installed on the Macintosh HD but am not sure whether to move it).

I have looked up second HD and installation on Google, but what I found was about installing OS X on a second boot drive, not quite what I was looking for!

My question is, basically: Will applications run well off a second drive, and is this a good idea before I even do it?

I'm fairly new to OS X, got better since I started on it in mid-2012, any advice is much appreciated!
Mac apps run pretty much anywhere you care to store them.

Unfortunately, most Mac apps are also so small that the time you spend moving them off the boot drive doesn't compensate for the amount of space you recover.

You might look to store things like video and then photos and last music off the main volume as they typically take far more space.

As long as you don't have two copies of an app, you are free to quit any app and move it on or off the main volume as you please so other than losing some time, you can start now and see if this plan helps you reach your storage goals or if you need to reexamine them once you've moved all the apps you care to relocate.