or, a fair bit before show time, load the tape, record a bit, rewind back to beginning and hit play. If you see levels, you know the tape loaded properly.
Then, when you're ready to "really" start recording, play the tape back again. Once you see levels, hit pause and then hit record -- since the tape will not unload after playback (where it was showing levels), you can be pretty confident that the tape's in fact loaded and ready to roll.