I’ve written a comprehensive list of tips for preparing for Bett in order to get the best experience. That will appear on this website (ICT & Computing in Education) on 17 January 2020 at 5:30 am.
In the meantime, this guide from Seced is worth looking at. There’s an interesting research article by Caroline Wright from BESA, a guide to the zones, and an incisive article from fellow Bett veteran Bob Harrison. Obviously, read the other sections too, such as the guide to surviving Bett, by Dave Smith, but if you’re pushed for time start with those three.