I've done a few sessions there now and it is great fun.
Just listen to the coach at the start and do as he says, that way as long as he sees your listening and your competent, before you know it you'll have the run of the track.
Always shoulder check before changing lanes, (up or down), and keep aware that not everyone picks it up as quickly as others, and if your not used to riding fixed then take some time to get used to scrubbing your speed in preparation of stopping.
It's all common sense and the coach was very informative the first time I went, when you go back again just tell him you've been before and he'll let you on the track straight away IME.
A few guys on here organise track session at Manchester from time to time, so keep your eyes peeled in the
RIDES section for any upcoming ones
@colly tends to organise them IIRC and also going off
THIS post from last year