Negotiating too early: Wait until you have a written offer as premature asks weaken your leverage.
Skipping research: Use current market data (role, location, industry) to anchor your range.
Focusing only on base pay: Evaluate total compensation (bonus, equity, PTO, flexibility, development, review timeline).
Being vague or emotional: Make a clear, evidence-based ask with a specific number or narrow range.
Over-countering repeatedly: One thoughtful counter (two max) is professional; dragging it out can sour the tone.
Not getting it in writing: Confirm all terms (title, duties, pay, perks, start date, review timing) before accepting.