The first 90 days for a startup are critical. This is where you validate your assumptions, find your first customers, and prove that your idea has legs.
Week 1-30: Validation
Don't build anything yet. Talk to 50 potential customers. Understand their pain points at a deep level. Your initial assumptions are almost certainly wrong — that's okay.
Week 31-60: Build & Iterate
Build the smallest possible version of your product that tests your core hypothesis. Launch it to your waitlist and collect feedback obsessively.
Week 61-90: Acquire & Retain
Focus on channels that don't scale first. Do things manually. Send personal emails. Give high-touch onboarding. Learn what makes users stay before you try to grow.