I finally got a multimeter after 9 years of guessing, and the first thing I tested was a dead outlet in my garage
For 9 years I just flipped breakers and hoped for the best. Last week I grabbed a $22 Klein at the hardware store in Spokane and found the outlet was reading 40 volts, not 0, which meant a loose neutral behind the wall. I almost stuck my hand in there and called it safe just because the lamp was off. Turns out my whole garage run was daisy chained off one weak wire nut. What would you check first with a meter if you were starting from scratch?
Checking the voltage first was smart, but the thing almost nobody does is test with a load on the circuit. A loose neutral like yours can read a normal 120 with the meter alone since it draws almost no current, then drop to nothing the second something actually pulls power. Plug a lamp or a phone charger in and read the outlet while it's on, and you'll catch weak connections a plain voltage test hides. Same trick works on the breaker panel, a reading can look fine until a real load hits it. That weak wire nut would've probably shown itself right away with a $5 outlet tester and a lamp plugged in.