The best thing to do is vary your rpms... the worst you can do is go on a long drive with the cruise set at one speed. You want to break in the whole power band.
The 2009 Owners Manual (p 72) has the following to say about the break-in period:
-- ENGINE BREAK-IN RECOMMENDATIONS
A long break-in period is not required for the engine in
your vehicle.
Drive moderately during the first 300 miles (500 km).
After the initial 60 miles (100 km), speeds up to 50 or
55 mph (80 or 90 km/h) are desirable.
While cruising, brief full-throttle acceleration within the
limits of local traffic laws, contributes to a good break-in.
Wide-open throttle acceleration in low gear can be detrimental
and should be avoided.