Someone just came back from a conference saying you need to fine-tune your AI model. Your IT team is asking about RAG. A consultant says better prompts would solve everything. They might all be right — for different problems. Here's what each approach actually does and when it makes sense.
Prompting: Start here, almost always
Prompting is giving AI clear instructions and context at the moment you interact with it. 'You are the customer service voice for our company. We have a friendly, direct tone. Here are our return policies. Answer this customer question...' That's a prompt. For most small and mid-sized businesses, sophisticated prompting solves 80–90% of customization needs without additional technical investment. Before anything else, write better prompts.
RAG: When AI needs to know your stuff
RAG stands for Retrieval-Augmented Generation. In plain English: the AI searches your documents before answering a question. Instead of relying on its training data, it pulls from your product manuals, client files, policy documents, or internal knowledge base. The result is answers grounded in your actual content. RAG is the right move when you have a defined body of knowledge you want AI to use — without baking it permanently into the model. It's the most common 'step two' for businesses that have outgrown prompting alone.
Fine-tuning: Rare, specialized, expensive
Fine-tuning means retraining a model on your own data to change its core behavior — teaching it to speak in a specific industry dialect, or to excel at a narrow task it wasn't originally built for. It's expensive, technically demanding, and usually overkill for SMBs. The cases where it genuinely makes sense are narrow: highly specialized domain knowledge that can't be captured in prompts or documents, or extremely high-volume applications where every marginal quality gain has real financial value.
The honest take
Most businesses should start with prompting. If they hit a ceiling, RAG is the logical next step. Fine-tuning should be a last resort or a choice made with very specific business justification. If a vendor is pitching fine-tuning on your first conversation, ask why prompting wouldn't work instead. It's a reasonable question, and a good vendor will have a real answer.