Principles of war
These principles are:

Restraint – to limit collateral damage and prevent the unnecessary use of force. Restraint requires the careful and disciplined balancing of the need for security, the conduct of military operations, and the national strategic end state.
Perseverance – to ensure the commitment necessary to attain the national strategic end state. The underlying causes of the crisis may be elusive, making it difficult to achieve decisive resolution. The patient, resolute, and persistent pursuit of national goals and objectives often is essential to success.
Legitimacy – to maintain legal and moral authority in the conduct of operations. Legitimacy, which can be a decisive factor in operations, is based on the actual and perceived legality, morality, and rightness of the actions from the various perspectives of interested audiences.
Together, these 12 concepts form the Principles of Joint Operations.

Canada: The Canadian Armed Forces principles of war/military science are defined by the Royal Military College of Canada or Canadian Forces College website to focus on principles of command, principles of war, operational art and campaign planning, and scientific principles.

principles of command – Lead By Example; Know Your subordinates And Promote Their Welfare; Develop Leadership Potential; Make Sound And Timely Decisions; Train subordinates As A Team; Communicate Ideas Clearly; Keep subordinates Informed Of All Activities And New Developments; Take Initiatives; Know Yourself And Pursue Self-Improvement; Treat subordinates As You Wish To Be Treated
principles of war – Selection and maintenance of the aim; maintenance of morale;  offensive action; surprise; security; concentration of force; economy of effort; flexibility; co-operation; and administration. These principles are not listed in any order of importance.
operational art and campaign planning – the organization and synchronization of the planning process and maritime, land and air forces.
scientific principles – involved in military reconnaissance, surveillance, and target acquisition in the context of military operations.

France: The French Army recognizes three principles to be applied to operation of land forces at the tactical level:

Freedom of action – "The ability of a commander to use his means at any time and to act despite the presence of the enemy and the various constraints imposed by both the environment and circumstances, in order to achieve the assigned goal. [...] Freedom of Action consists of maintaining the initiative with regards to the enemy in order to 'control upcoming action' and seize opportunities."
Unity of effort – "Convergence in space and time of actions and effects of the different operational functions. [...] Unity of Effort distinguishes itself from the concentration of forces through the need to combine actions and optimize effects in order to increase the effectiveness on the chosen objective." This principle includes the psychological effects of surprise and troop morale, in addition to the more conventional principle of concentration of forces.
Economy of means – "Proper distribution and use of assets in order to obtain the best ratio of capabilities vs. effects in order to achieve the assigned goal." The instruments for this principle are modularity, the "task organization" of the forces, and support.
According to French doctrine, new principles should be observed, primarily to protect the principle of "Freedom of Action":

Legitimacy – Among the local population,  in national public opinion, and among international institutions.
Necessity – The appropriate amount of force is to be used for each desired objective.
Reversibility – The military actor should be prepared to quickly change its course of action depending on the opponent's attitude. Organize military actions to limit human losses and material damages. Remain open to opportunities for de-escalation, and prepare to "support the failure of the enemy" rather than needlessly seeking total destruction. "[Keep] the operation’s level of intensity as low as possible."

Israel: The principles of war according to Israeli doctrine are:

Maintenance of the aim;
Morale;
Initiative;
Stratagem;
Concentration of effort;
Security;
Optimal utilization of force;
Continuity;
Depth and reserve;
Simplicity.

People's Republic of China: The military principles of war of the People's Liberation Army were loosely based on those of the Soviet Union until the 1980s when a significant shift begun to be seen in a more regionally-aware, and geographically-specific strategic, operational and tactical thinking in all services. The PLA is currently influenced by three doctrinal schools which both conflict and complement each other: the People's war, the Regional war, and the Revolution in military affairs that led to substantial increase in the defence spending and rate of technological modernisation of the forces.

People's war – which is derived from the Maoist notion of warfare as a war in which the entire society is mobilized
Regional war – which envisions future wars to be limited in scope and confined to the Chinese border
Revolution in military affairs – which is a school of thought which believes that technology is transforming the basis of warfare and that these technological changes present both extreme dangers and possibilities for the Chinese military.
In recent years, 'Local war under high-tech conditions' has been promoted.

Other uses: These principles can be applied to non-military uses when Unity of command is separated into coordination and reality, Economy of Force is redefined as use of resources, Mass is separated into renewable and non-renewable resources, and relationships are separated from unity of command.
In 1913 Harrington Emerson proposed 12 principles of efficiency, the first three of which could be related to principles of war: Clearly defined ideals – Objective, Common sense – Simplicity, Competent counsel – Unity of Command.
Some of the twelve non-military principles of efficiency were formulated by Henry Ford at the turn of the 20th century, and are suggested to be: objective, coordination, action, reality, knowledge, locations (space and time),things, obtaining, using, protecting, and losing. Nine, ten, or twelve principles all provide a framework for efficient development of any objective.
Principles of War was also a book published in 1969 for the Japan Self-Defense Forces. It outlines the basic military principles and strategies by which the Japanese army was to operate. The book was used for most military exams in Japan. The book backs up all military principles with historical examples.

See also: Geneva Conventions
Grand strategy
Hague Conventions
Military doctrine
Military strategy
Military tactics
Naval strategy
Operational mobility
Principles of sustainment
Strategy
U.S. Army Strategist

Notes and citations: 

References: von Clausewitz, Carl, The most important principles of waging war to complete my course of instruction for his Royal Highness the Crown Prince (German: Die wichtigsten Grundsätze des Kriegführens zur Ergänzung meines Unterrichts bei Sr. Königlichen Hoheit dem Kronprinzen), 1812 Translated and edited by Hans W. Gatzke as "Principles of War, September 1942, The Military Service Publishing Company
Emerson, Harrington, Twelve Principles of Efficiency, Kessinger Publishing, 2003
Van Avery, Chris, LCDR, USN, 12 New Principles of War, Armed Force Journal, The Defense News Media Group, July 2007 [2].
West, Joseph, Dr., Principles of War: A Translation from the Japanese, U.S. ARMY COMMAND AND GENERAL STAFF COLLEGE, FORT LEAVENWORTH, KANSAS, 1969 [3]
Frost, Robert S., Lt.Col. (USAF), The growing imperative to adopt "flexibility" as an American Principle of War, Strategic Studies Institute, U.S. Army War College, Carlisle, PA, October 15, 1999 [4]
Storper, Michael & Scott, Allen John, Pathways to industrialization and regional development, Routledge, 1992
Corbett, Julian Stafford, Sir, Some Principles of Maritime Strategy, London, 1911, US Naval Institute Press, 1988 (The Project Gutenberg eBook [5])
Glantz, David, Soviet Military Operational Art: In pursuit of deep battle, Frank Cass, London, 1991