The complete 2026 developer guide to fine-tuning LLMs — 15 chapters covering why and when to fine-tune, hardware & cloud GPU options, dataset preparation and quality, full fine-tuning vs parameter-efficient methods, LoRA and QLoRA deep dives, fine-tuning with Unsloth, alignment via RLHF/DPO/ORPO, evaluation metrics, merging & quantizing, deployment with vLLM/TGI/Ollama, cost analysis and ROI, and real-world case studies.