In short, the task being performed will determine the standard of care imposed. The usual starting point is that the defendant must behave as a reasonable man would in all the circumstances. The classic description of the standard of care was given by Alderson B in Blyth v Birmingham Waterworks (1856) 11 Exch 781:

Negligence is the omission to do something which a reasonable man, guided upon those considerations which ordinarily regulate the conduct of human affairs, would do, or doing something which a prudent and reasonable man would not do.