Utilitarianism is the moral policy that the right or ethical action in any circumstance is the action that results in the best outcome. Though there are several practical difficulties with utilitarianism, I think that it is still practicable in real life.
First, I'll need to define what practicable means. Amongst all the ethical theories, utilitarianism is the most difficult to implement and requires the most judgment. Rule-based or intent-based systems are considerably simpler for a moral agent to follow, since no moral calculation is generally required. Furthermore, utilitarians need to constantly assess each and every potential action, many of which may be irrelevant under different ethical systems, in order to obtain the "best" outcome. This cannot be considered as being practicable, as it requires mental and predictive capabilities far in excess of human capacity. I will also argue that spending time considering ethical decisions has a corresponding cost, by diverting time away from other positive actions. Therefore, in practical terms, a simplified form of utilitarianism is necessary.
It is wiser then to restrict the theory to what a human can reasonably do. The most obvious way is to rely on a rules-based framework. This framework consists of a set of moral principles or rules, much like deontological ethics. However, the rules are ultimately grounded in utilitarian principles and can be derived from utility calculus, averaged for general circumstance. Therefore, a person following this form of rule utilitarianism believes that by following these moral guidelines, utility is increased on average. Also, rule utilitarianism does not require strict adherence to the ethical principles proposed; it is consistent to violate some lesser principle, which on average yields better outcomes, if it is reasonably clear that the violation results in greater utility.