Azure offers six primary VM types: General Purpose for balanced workloads, Compute Optimized for CPU-intensive tasks, Memory Optimized for data processing, Storage Optimized for high disk throughput, GPU Accelerated for graphics and AI workloads, and High Performance Compute (HPC) for scientific computing. Choosing the right category depends on your specific workload requirements and performance needs.

Start by clearly defining your workload requirements including CPU, RAM, disk I/O, and network needs. Use the interactive Azure VM Size Selector tool to match these requirements with appropriate VM sizes, then perform performance testing with load, stress, and soak tests before full deployment. Monitor your VMs after deployment using Azure Monitor and Advisor to identify optimization opportunities.

Key factors include vCPU count, RAM capacity, disk type (Standard HDD, Standard SSD, Premium SSD, or Ultra Disk), deployment region, and historical performance data if available. You should also evaluate different pricing options such as Pay-As-You-Go, Reserved Instances, and Spot pricing to optimize costs.

Yes, Azure allows you to resize VMs based on actual usage trends and performance monitoring data. By continuously monitoring your deployment with Azure Monitor and Advisor, you can identify when resizing or optimization is needed to better match your workload demands.

Azure offers four disk type options: Standard HDD for non-critical workloads, Standard SSD for moderate performance needs, Premium SSD for high-performance applications, and Ultra Disk for the most demanding I/O-intensive workloads. Your choice should align with your application's performance requirements and budget constraints.