Simple advice for anyone haggling over a house or a paycheck: never walk in without doing your homework.

• The biggest mistake in any negotiation is going in blind, with no idea what things are really worth.
• On a home, that means checking what similar houses actually sold for instead of trusting the list price.
• It also means learning the other side's position — like how many other offers a seller has, if any.
• No competing offers is a signal the place may be overpriced, giving you room to bid lower.
• Whoever has the most information wins; without it, you lose almost every time.

Outlook: Buyers and job-seekers who research comps and the other side's situation before making an offer will consistently come out ahead.