(a) Height - what is the minimum working height you need - think about the fact that some industrial units will have a flat roof. Also think about steel frame construction so height to the underside of the frame. Height is more appropriate when considering warehouse units.
(b) How many loading doors do you need - again perhaps more critical for warehouse property - and height of the doors - do you need articulated lorries to back in?
(c) What sort of/number of lorry movements do you have and the size of lorries that you use or are to visit?
(d) What office space do you need? / How many office staff are employed?
(e) How many car parking spaces are required? - something more critical when looking at office property!
(f) Do you have a specific power requirement? If it is excessive you need to think about power availability in the area.
(g) Do you need a dedicated yard area - this often reduces the number of suitable properties as detached units are in shorter supply.
Help us to help you. Identify your requirements in detail from the outset and your relocation should be easier to implement.