For some conditions I tell my patients “red flags” to look out for. These are symptoms that mean your condition has become more serious and needs urgent (A&E) treatment.
In my job the main ones I tell people to look out for is changes in bladder or bowel function (e.g. incontinence) and numbness in the genital region.
It also helps to know the natural course of your condition. For example as with sciatica, you may get more back pain as the leg pain gets better - this is actually a good sign!