A curved blade fork pushed back as from a crash is very easy to diagnose.

Stand next to the bike with the wheel pointing forward. Bend over and sight down the steerer/headtube and out the the blades. The blades will clearly be in line with the sight line until about half way down where they curve forward. If you can't see the error, then the fork os fine.

Straight blade forks are harder to diagnose this way, but they rarely bend in the blades, so you're only looking for a bent steerer which will manifest by a crown race that isn't concentric to the lower cup. Rotate the fork and look for the crown race to appear to emerge or recede into the cup. (it shouldn't). You'll also usually (but not always) have a headset that binds a bit when turned to either or both sides.