• Daily stand-ups — This is the easiest practice to implement.  It requires no tools, little training, and rarely gets push-back from anyone.  The important thing to remember here is that these are for the benefit of the team members.  Be vigilant that the stand-ups don’t degrade into old-fashioned status meetings, where the team members address the manager, rather than each other.
• Product backlog — Beyond the importance of just having a prioritized backlog to begin with, it’s important that any given team works from a single backlog.  It’s okay for multiple teams to pull from the same backlog, but not vice versa.  That is, it’s not okay for a single team to have to deal with conflicting priorities from multiple sources.
• A well-defined, shared vision — In general, Agile is all about fostering better communications, which starts with a clear, meaningful goal.  Ask any team member, “Why are we here?”  His or her answer should be immediate and clear (but not by rote).
• Demos and feedback — This one is my nomination for the most important aspect of Agile.  It’s certainly the most important aspect of running a sprint cycle.  Whether you decide on using 2, 3 or 4 week sprints, and before getting good at playing planning poker, preparing burn-down charts, tracking velocity, and all the rest, be sure the team gets good at demonstrating their work and gathering feedback.  This one act connects the team with the rest of the organization like nothing else.
• Continuous integration — The four practices mentioned above apply to any type of project, but when it comes to software development projects, specifically, experts agree the number one best practice to rely on is continuous integration.  Using a tool like Hudson or Cruise Control, the software is automatically built and tested, either on a nightly basis or even more frequently as code is committed.

One last pearl of wisdom: On the question of whether to go with 2, 3 or 4 week sprints, the consensus is to go long.  Start with 4 or 3 week sprints.  Eventually, after you get the cadence down and all of the agile practices are built up, you can think about shortening the sprint cycle to 2 weeks, or even 1.  It’s like learning how to drive a car.  At first, driving at freeway speeds can be scary fast, but then you get used to it, even to the point where driving 55 MPH seems painfully slow.