How can I tell if I have root? I've been attempting to root my phone (Samsung Intercept M910, but that probably doesn't matter).

How can I tell that I have actually, successfully gained root? I've run a few apps which require root, and some work and some don't, so I'm unclear if I've gained root or not.
Use terminal emulator (a popular free/open-source terminal emulator is Android Terminal Emulator, available from F-droid or Play Market), open the emulator and type 

su

you will know with the message that appears after if phone is rooted or not.

Edit:

There is an app just for this now : Root Checker