Strategy for Employee Historical Data Migration to SAP from Legacy

Dear Friends,

Are there any SAP recommended best practice for Employee PA, OM, Time and Payroll Historical Data Migration to SAP from Legacy?

What are you all best advices and leranings from your own SAP HR implementation?

Not able to decide on any cutover strategy and how much data to take into SAP. I am very much confused and tensed related to Payroll and Time Data takeover.

The client is a SPanish client and their Fiscal Year is starting from 1st January and mine Go-Live date is 1st April.

Please pour in your suggestions. Lets make this thread a bible for every SAP HCM consultant working on Implementation.

Thanking You.

Sunny Singh