What's the best way to negotiate a raise or a starting salary?

Negotiate with data, not feelings. Before the conversation, research market pay for your role, level, and city using sites like Levels.fyi, Glassdoor, or Payscale, and write down two or three specific accomplishments that show your impact. For a starting offer, almost always counter once politely – many employers expect it and build in room. Anchor with a number slightly above your target, then let them meet you. For a raise, time it near performance reviews or after a clear win, and frame it around the value you deliver, not your bills. If they can't move on base, negotiate a signing bonus, more equity, or extra PTO. The worst they say is no, and asking professionally rarely costs you anything.