Desktop: it is necessary to have identical systems for software. Installing a single sign-on for users and roaming users in order to have a personalised user profile available is a key step.
Applications: special configuration for use within a hot-desk or remote environment may be required, and this will depend on the desktop. More bandwidth will be needed.
Server: more storage space should be made available in order to facilitate storing personal files.
Telephone: you need a PBX system in which users log into any phone, using their designated extension number; all calls to their extension number will be directed to that handset. The same applies for faxes, but a problem remains with multiple sites which do not have the software, or when users are working from home.
Integrated messaging: such systems solve the difficulties of collecting voice and fax messages from different locations.