To start altcoin development, first identify a unique use case that differentiates your coin from thousands of others. Are you solving scalability issues, enabling niche applications, or creating a governance-focused token? Next, choose the right blockchain architecture building on Ethereum or creating your own chain using Cosmos SDK or Substrate. Develop smart contracts or core protocols with security and scalability in mind. Tokenomics planning is critical for long-term sustainability. Finally, test rigorously and prepare a marketing strategy to build community and investor interest.