RAML (RESTful API Modeling Language) is a popular API description format used by developers to design their APIs from scratch. It offers features like reusable libraries, traits, and more. However, RAML files can be prone to mistakes, especially for developers who are new to the format. Common mistakes include referencing components that don't exist, incorrect paths or invalid file names, not defining types or traits in referenced files, trying to reference a RAML type in a JSON schema, using invalid YAML formatting, and failing to follow the RAML specification. These errors can cause conversion failures when using tools like Transformer. To avoid these mistakes, it's essential to follow the RAML specifications carefully and use tools that validate RAML files for free.