Most people only notice a socket is a problem once something's already gone wrong. The good news is there are usually warning signs well before that point, if you know what to look for.
Start with how it looks. Scorch marks or brown discolouration around the socket face or the pins of a plug are a serious sign, they mean arcing or overheating has already happened, not that it might happen someday. A cracked or chipped faceplate is worth taking seriously too, since it can expose parts that were never meant to be touchable.
Next, how it feels and sounds. A socket that's warm to the touch, especially without an obvious reason, shouldn't be ignored. The same goes for any buzzing, crackling, or sizzling sound when something is plugged in or unplugged, and definitely any visible sparking.
A socket that feels loose, where a plug wobbles or doesn't sit snugly, often means the internal connections have worn over time. Smaller warning sign on its own, but worth having looked at.
Overloading is a common, avoidable cause behind a lot of this. A standard UK socket is rated at 13 amps, roughly 3,000 watts. Running several high draw appliances through one extension lead, or daisy chaining multiple leads together, pushes well past what it was ever designed to carry.
If you spot any of the signs above, the safest move is to stop using that socket and get it looked at.