This is not a question but a tip for anyone as noob-ish as myself. This hasn't been mentioned in the forum before so far as I can see, so probably this is '[expletive deleted] obvious' to more experienced users.

A workmate and I recorded five screen tutorials yesterday but were disappointed to find that only two of them had any audio.

The problem was that we were re-plugging the (USB) microphone into the computer too late in the launch sequence for recording a new video.

Basically, always ensure the microphone is plugged in before you hit the Record button: do not wait until after you have selected the window you want to record, because you will be wasting your time.