12. Say no or yes, no matter the request
The last, best way to ensure IT failure is to say no or yes, no matter the request. Say no, and you damage your relationships. Say yes, and you're making promises you can't keep because you and everyone else already have all your time fully accounted for.
The right answer if you want to succeed: "We can do that. Here's what it will take."
There's an inviolable rule of request management, whether the request is a project scope change, a software enhancement, or providing a laptop to someone not scheduled to receive one: Nothing is ever free.
Don't say no. Don't say yes. Explain what you'll have to do to satisfy requests. What follows will be a conversation rather than an argument -- a much better scenario.