Agile, where to start...

This is not the end-all-be-all silver bullet answer... but I answer this way because it is what others have shared, I have learned, and there is more support with these approaches.

If you are adopting Agile bottom-up from a tech team perspective... start with XP. If you are adopting agile top-down from a business perspective, start with Scrum.

And yes, at Agile 2008 in Toronto, during the keynote banquet Uncle Bob Martin basically declared that XP and Scrum need to unite and that they complement each other. I attribute this to the fact that XP focuses on engineering practices and Scrum focuses on PM approaches. Someone at ObjectMentor once told me that XP is the content and Scrum is the box it ships in.

Why is the previous in quotes? Because it was part of a discussion that I contributed to Peter Stevens description of what is agile after he attended an agile conference in London. I do agree with him that there might be too many flavors, many mis-applied labels, and that Lean is a great complement to the above.