Begin by replacing VoIP in a self-contained part of the business then gradually extend its use.
Encourage staff involvement and feedback, this will help smooth implementation, as staff buy-in can make or break a technology project.
Consider setting up a cross-departmental taskforce to manage the implementation process - it will help with staff buy-in and ensure that implementation works company-wide.
EVALUATE
Monitor and review the impact on your business and against your objectives.
Monitor quality of service and network availability.
Get feedback from staff, customers and suppliers on the changes.
Evaluate the impact after six months and one year. Have you achieved your objectives? Establish how you could improve things further.