IT axioms
Some IT management axioms I work by:
1) Practices* are what we in IT do. Technology is what we do it with. Clearly practices are at least as important as the technology. In fact, to me it is obvious that practices are more important. Practice is the action, technology only the tool. Both are essential, but the practices are where we should focus our attention for management, control and improvement. Tennis is not about tennis racquets. [Any techs who don't get this need to be reformed, removed or restrained.]
2) Now I want to go through that entire argument again but with people and practices. People drive both practices and technology. Practices are just a way of describing behaviour of people. No people, no practices. A key point: you can try to change practices until you are blue in the face but if you don't change people's attitudes and culture you won't change practices. People are the second most important element of all in IT. [Process geeks who don't get this litter the world with useless manuals. They need to be enlightened, ignored or neutralised.]
3) "Second most"? Yes, customers are who we do the practices for. They are the reason, the motivation, and the measure of success. [We all need reminding of this on a regular basis.]
4) IT delivers services. Services are what comes out of the pipe: services are consumed by users and paid for (directly or indirectly) by customers. No consumer or no exchange of value => not a service. We should value and prioritise what we do in IT by how it contributes directly or indirectly to delivery of service. [If the service doesn't care then we shouldn't]
5) IT is measured by its efficiency and effectiveness. All improvement is about improving efficiency and/or effectiveness. [If you can't express it in those terms they you aren't improving anything].
I'm sure there are many more fundamental axioms of ITSM. Suggestions?
* What I call "practices" are "processes" to ITIL and to many readers. But "process" means something specific: a repeatable series of steps with inputs and outputs. A "practice" (as in the usage "best practice") is a collection of roles, responsibilities, functions, policies, plans, procedures, tools and ... processes.
Made in New Zealand 
Comments
Simplicity
#6 Keep it simple, simplicity is good (I don't like the acronym KISS but it has a point)
#7 Be very careful when you tamper with the customer interface, i.e. the way the services interact with the customer. Customers remember failures and regaining lost trust is difficult.
Aale
Here's some suggestions:
1. Measure IT in terms that matter to the rest of the business. IT services are measured by the CUSTOMER's perception of efficiency and effectiveness relative to perceived value - costs and price matter.
2. IT is not a separate function from the rest of the business. IT's raison d'etre is enabling business practice improvement.
3. Engineer's view of perfection is often different from the business. Business wants evidence of steady improvement, they understand improvement. Spending to achieve perfection and blowing the budget, or delaying advances to achieve perfection, isn't good support for the rest of the business. This is an application of Voltaire's, "The perfect is the enemy of the good."
more axioms
I think your item #1 is an improved variant of my #4. Your #2 and #3 I missed completely. (#2 is actually 2 distinct axioms). #3 I call ETF: Excessive Technical Fastidiousness: techs must learn to live in an imperfect world of imperfect information.