Load-bearing walls almost always run perpendicular to floor joists

Before removing any interior wall, look at the joist direction from the basement or attic. If joists run perpendicular to the wall, it is likely load-bearing. If parallel, it is likely a partition wall. Confirm by checking for doubled-up joists or beams above/below. This 30-second check prevents the most dangerous DIY mistake in home renovation. Always get an engineer to verify before demolition.