Getting ready is involves two things:

• Learning about agile methods and concepts.
• Talking it up.

The Learning Phase
Read all you can about lean and agile concepts.  Mind you, a lot of what's out there isn't very helpful...it's too general.  But you'll get the idea of what it's all about and how the various pieces fit together.  If you can, talk with others in your industry that have implemented some or all of the agile tools.  Again, people who've implemented it tend to be very general in what they say (How come nobody can just say, "Here's exactly what we did.  Here's what worked.  Here's what didn't."?  Everyone, whether they're writing a book or giving a presentation want to tell you how important leadership commitment and involving employees is.) but look at the details and ask questions where you can. 

This learning won't necessarily give you an idea as to how to go about implementing an agile initiative but it will get you familiar with the concepts and tools.

Some folks spend a few months in this learning phase, others spend a few years.  It shouldn't take a few years.  Lean nor agile is that hard to figure out.

Talk It Up
Talk with your colleagues in the organization about agile concepts and methods.  Talk with employees.  You don't have to have a fully formed vision to start conversations about it all.  Have others read some of what you're reading. ( If you're the boss, make them read.  It's not like it will hurt them or anything.)  Send them to seminars, conferences and tours.  Tell others what you're learning and have them tell you (and each other) what they are learning. 

You need to make these phases part of your job.  Put things on your schedule even if it's just  "10am to 10:30am - Walk around and ask employees what frustrates them in their jobs and talk about how agile methods can reduce those."

Stuff like that.