Define the language goals
Choose the language paradigm
Design the syntax
Design the semantics
Define the data types
Define the control flow constructs
Define the scoping rules
Define the memory model
Define the error handling model
Write a formal grammar
Build a lexer
Build a parser
Build an abstract syntax tree
Build semantic analysis
Build an interpreter or compiler
Build code generation
Choose a target platform
Implement a runtime system
Implement a standard library
Implement input and output
Implement package management
Implement tooling
Implement a REPL
Implement diagnostics
Test the language
Benchmark performance
Document the language
Release the language
Maintain and evolve the language