I visited Naidex (disability show) at the NEC (for the first time). I travelled by train as the station adjoins the Exhibition Centre, but it is a vast area so be prepared for a long walk. Shuttle buses are often available for certain exhibitions – look for directions from the station.
Make sure you know which exhibitions hall(s) the event is in before you get there, and watch the signs very carefully. If you take a wrong turn it could mean an extra long detour. There is limited colour coding on the overheade signs, but it is still inadequate in my view. Where levels change there is a lift as an alternative to the escalator. Some long straight sections have a travelator, but beware when joing and leaving. You may choose to continue walking on the fixed pavement?
The interior passage ways are wide and well lit, but the decor is boring and dated. It certainly is a concrete jungle. The outside of the complex is much more attractive. Try to remember your route for the retuirn journey. I visited at a quiet time, but attending a concert or other large event could mean congestion before and after. Jostling crowds can be unpleasant!
Like any exhibition it can be very busy, and the heat and lights can be trying. Take a small bottle of water, and rest when you can. Mornings are often quieter than later in the day. Have a plan of the exhibition, and mark which stands you would like to visit. It is very easy to miss one, and then perhaps never find it again. Plan a systematic route around the exhibition to see as much as possible.
Visiting an event at the NEC can be very tiring, and remember you have got to get home afterwards. Refreshments can be very expensive!
Enjoy yourself though and maybe come again next year?