Understand the workload
List the applications, their dependencies and how people use them. Steady background tasks, busy transaction periods and large file operations place different demands on a system.
Separate the resources
Compute, memory, storage capacity and storage performance are different constraints. Record current use and peaks before choosing a size. A larger machine is not always the answer to a bottleneck.
Decide the boundaries
Document network access, account ownership, backup responsibilities and the services outside the core environment. A usable infrastructure plan includes these operational details.
Review the first period
Define how utilisation, errors and user experience will be reviewed after deployment. Record a sensible adjustment process rather than treating the first resource choice as permanent.
Bring the current environment and the outcome you need to a project enquiry. Use the capacity planner for a first cost model using your own provider rates.