It's not hard to unclip when the tension is "normal" . . .

As for beginner's tips, I would practice clipping in and out while the bike is moving (granted, I did this on a road bike, so this might actually not be such a good idea on a fixed bike cuz of the pedal rotation), so that you get used to the motion while you have momentum to keep you from falling.

Actually, before I did that even, I just sat on the bike where I could safely hold on to something (like in a doorway) and clipped in and out until I felt comfortable doing it in motion.