What are the essential things for an introduction to astronomy?

Today I had the opportunity to talk with a group of high school students in an astronomy class at University Schools, a charter school, up the road in Greely, CO. The last time I was around high school students was when I did some classroom observing as part of the education program at my undergraduate institution, Hastings College. The group came to DU's historic Chamberlin observatory as part of an outing to Denver.

 After Aaron gave them a tour of the building and discussed the various technical aspects of the telescope and structure, fellow DU graduate student Jamie Lomax and I discussed what it's like to go through college and choose a career in astronomy. The class instructor asked us some really good questions which made me realize that I really use the three-R's quite frequently and that mathematics and scientific procedure are just the highest-level things you need to do this sort of work.

So, this got me thinking.  What are the essential things that one needs to do astronomy/astrophysics?  With our community of teachers, amateurs, professionals, and newbies on here I thought we could actually start a good discussion about what one needs to know to do/understand astronomy/astrophysics in general. I hope that we can take the list that results from this discussion and make an "newbie" guide to astronomy out of it.

A few questions to get things going:

So, what are the most important concepts for someone new to astronomy/astrophysics? What vocabulary will help them digest our jargon? What are the best set of experiments one can do to understand astronomical research?  What other skills are essential to learning or understanding astronomy?  How important are mentors?