Define the language purpose
Choose the target users
Decide the language paradigm
Specify the syntax
Specify the semantics
Design the type system
Define the standard library
Choose an implementation strategy
Build a lexer
Build a parser
Build an abstract syntax tree
Build semantic analysis
Build an interpreter or compiler
Add error handling
Add memory management
Add runtime support
Add package management
Add tooling
Add testing
Add documentation
Add examples
Implement the first prototype
Test with small programs
Refine the language design
Optimize performance
Stabilize the language
Release the language
Maintain and evolve the language