IT Implementation User Awareness and Change Management

What do you think are good strategies to manage the change posed by IT implementations (Applications or systems like VOIP) so that awareness levels are high, user acceptance levels are high, and therefore the change over is smooth?

I am particularly interested in the various user awareness strategies including but not limited to user training - possibly broadcasts, targeted announcements, quick-tips, etc.. Also their relative merits and how to plan and execute them.

If and how do we include this as part of a change management process?

Thanks