a. Special requirements
Requests must include: The conduct, if it occurred in England and Wales or Northern Ireland, would constitute an indictable offence (dual criminality); There is material on premises which is likely to be of substantial value (whether by itself or together with other material) to the investigation of the offence; The material would be relevant evidence; and The material does not consist of or include items subject to legal privilege, excluded material or special procedure material; It is not practicable to communicate with any person entitled to grant entry to the premises; or Although it is practicable to communicate with a person entitled to grant entry to the premises it is not practicable to communicate with any person entitled to grant access to the evidence; or Entry to the premises will not be granted unless a warrant is produced; or The purpose of a search may be frustrated or seriously prejudiced unless a constable arriving at the premises can secure immediate entry to them.
b. Other useful information
Where possible agents of the requesting state should request participation in the search. The link below gives information for competent authorities abroad about obtaining evidence within the UK (or abroad) to assist in criminal investigations or proceedings: https://www.gov.uk/guidance/mutual-legal-assistance-mla-requests