Performing P2V best practice

I am planing a Large project P2V and V2V. (DCs, SQL server, Exchange,RDS server). Almost 30 servers (Consolidation)

Please What are the best practise before and after P2V or V2V.

I am looking for more like a real life discussion answers - more like what you have done when you performed either conversion.

Please feel free to drop comments

Thanks Guys..